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• 41. [Article] Processing effects on the ductility of chromium-vanadium alloys

  The next generation of high temperature structural alloys must exhibit exceptional resistance to fracture, creep, oxidation, and fatigue at high temperatures. Chromium is being considered due to its high ...

  Citation × Citation Citation Abstract Copy Title: Processing effects on the ductility of chromium-vanadium alloys Author: Murdock, Hailey M. The next generation of high temperature structural alloys must exhibit exceptional resistance to fracture, creep, oxidation, and fatigue at high temperatures. Chromium is being considered due to its high melting point (>1800°C), relatively low density (~7.2 g/cc), high temperature strength, and oxidation resistance. Limiting the use of chromium is its high ductile-to-brittle transition temperature. Previous efforts to reduce the ductile-to-brittle transition temperature have considered elimination of embrittling interstitals, increasing the grain size, pre-deformation and alloying. Recent computational studies have renewed interest in using alloying additions to ductilize chromium. A series of first principles calculations recently revealed elements (Ti, Zr, Hf, Nb, V) which have potential to reduce the ductile-to-brittle transition temperature when alloyed with chromium. To experimentally measure the effects of alloying and processing on the ductile-to-brittle transition temperature, chromium-vanadium alloy samples of 3 different compositions were prepared and compared to nominally pure chromium. Chromium vanadium samples were prepared from powders, hot isostatically pressed, heat treated at 1300°C and extruded at 1200°C. Elevated temperature Vickers hardness, elevated temperature tensile and elevated 3-point bend tests were performed. A diffusion study was performed using microprobe analysis to assist in the development of homogenization procedures for the alloys. Fracture surface analysis of bend and tensile specimens was used to determine the mode of fracture in bend and tensile specimens. Elevated temperature tensile tests determined a relationship between temperature and ductility in 100%Cr and 25%Cr-75%V alloys. Results from elevated temperature Vickers hardness suggest alloying with vanadium increases the strength by a factor of two. Premature failure in elevated temperature 3-point bend specimens and elevated temperature tensile tests made it difficult to quantify the effect of vanadium in affecting the ductility of chromium. Electron microscopy observations indicate that mechanical damage, likely caused by extrusion, is responsible for initiating the premature failures. Despite this complication, evidence of micro- and macro-scale ductile fracture mechanisms on the fracture surfaces of the Cr-V alloys indicate that the addition of vanadium indeed improves the ductility of chromium. Title: Processing effects on the ductility of chromium-vanadium alloys Author: Murdock, Hailey M. The next generation of high temperature structural alloys must exhibit exceptional resistance to fracture, creep, oxidation, and fatigue at high temperatures. Chromium is being considered due to its high melting point (>1800°C), relatively low density (~7.2 g/cc), high temperature strength, and oxidation resistance. Limiting the use of chromium is its high ductile-to-brittle transition temperature. Previous efforts to reduce the ductile-to-brittle transition temperature have considered elimination of embrittling interstitals, increasing the grain size, pre-deformation and alloying. Recent computational studies have renewed interest in using alloying additions to ductilize chromium. A series of first principles calculations recently revealed elements (Ti, Zr, Hf, Nb, V) which have potential to reduce the ductile-to-brittle transition temperature when alloyed with chromium. To experimentally measure the effects of alloying and processing on the ductile-to-brittle transition temperature, chromium-vanadium alloy samples of 3 different compositions were prepared and compared to nominally pure chromium. Chromium vanadium samples were prepared from powders, hot isostatically pressed, heat treated at 1300°C and extruded at 1200°C. Elevated temperature Vickers hardness, elevated temperature tensile and elevated 3-point bend tests were performed. A diffusion study was performed using microprobe analysis to assist in the development of homogenization procedures for the alloys. Fracture surface analysis of bend and tensile specimens was used to determine the mode of fracture in bend and tensile specimens. Elevated temperature tensile tests determined a relationship between temperature and ductility in 100%Cr and 25%Cr-75%V alloys. Results from elevated temperature Vickers hardness suggest alloying with vanadium increases the strength by a factor of two. Premature failure in elevated temperature 3-point bend specimens and elevated temperature tensile tests made it difficult to quantify the effect of vanadium in affecting the ductility of chromium. Electron microscopy observations indicate that mechanical damage, likely caused by extrusion, is responsible for initiating the premature failures. Despite this complication, evidence of micro- and macro-scale ductile fracture mechanisms on the fracture surfaces of the Cr-V alloys indicate that the addition of vanadium indeed improves the ductility of chromium. Close

• 42. [Article] Interaction and behavior of the redside shiner (Richardsonius balteatus) and the steelhead trout (Salmo gairdneri) in western Oregon : the influence of water temperature

  Water temperature influenced interactions between redside shiners and juvenile steelhead trout (≥1+) in the field and the laboratory. Distribution of the two species within various habitats was determined ...

  Citation × Citation Citation Abstract Copy Title: Interaction and behavior of the redside shiner (Richardsonius balteatus) and the steelhead trout (Salmo gairdneri) in western Oregon : the influence of water temperature Author: Reeves, Gordon H. Water temperature influenced interactions between redside shiners and juvenile steelhead trout (≥1+) in the field and the laboratory. Distribution of the two species within various habitats was determined in three streams with different water temperature regimes. The range of habitats occupied by trout in allopatry at cool temperatures and at intermediate temperatures in sympatry was similar but habitats occupied by shiners in allopatry at warm temperatures and in sympatry at intermediate temperatures differed. Shiners at warm temperatures in allopatry inhabited areas of intermediate depth and high velocity, similar to those inhabited by trout in the other streams. In the presence of trout at intermediate temperatures, shiners were found in deep, slow water. Water temperature and the presence of the other species influenced production, activity, and distribution of both trout and shiners in laboratory streams. Trout dominated at cool temperatures (12-15°C) and shiners prevailed at warm temperatures (19-22°C). The redside shiner exhibited two basic social organizations, loose aggregations and defense of an area. The type of organization observed varied with water temperature, abundance of food, and presence or absence of juvenile steelhead trout. The behavioral repertoire of the redside shiner was diverse. Size of the individual and proprietorship of an area were important in determining outcomes of interactions. Intensity of individual encounters varied with conditions in the laboratory streams. Plasticity of its social behavior appears to contribute to the ecological success of the redside shiner. Title: Interaction and behavior of the redside shiner (Richardsonius balteatus) and the steelhead trout (Salmo gairdneri) in western Oregon : the influence of water temperature Author: Reeves, Gordon H. Water temperature influenced interactions between redside shiners and juvenile steelhead trout (≥1+) in the field and the laboratory. Distribution of the two species within various habitats was determined in three streams with different water temperature regimes. The range of habitats occupied by trout in allopatry at cool temperatures and at intermediate temperatures in sympatry was similar but habitats occupied by shiners in allopatry at warm temperatures and in sympatry at intermediate temperatures differed. Shiners at warm temperatures in allopatry inhabited areas of intermediate depth and high velocity, similar to those inhabited by trout in the other streams. In the presence of trout at intermediate temperatures, shiners were found in deep, slow water. Water temperature and the presence of the other species influenced production, activity, and distribution of both trout and shiners in laboratory streams. Trout dominated at cool temperatures (12-15°C) and shiners prevailed at warm temperatures (19-22°C). The redside shiner exhibited two basic social organizations, loose aggregations and defense of an area. The type of organization observed varied with water temperature, abundance of food, and presence or absence of juvenile steelhead trout. The behavioral repertoire of the redside shiner was diverse. Size of the individual and proprietorship of an area were important in determining outcomes of interactions. Intensity of individual encounters varied with conditions in the laboratory streams. Plasticity of its social behavior appears to contribute to the ecological success of the redside shiner. Close

• 43. [Article] Amplification and dampening of soil respiration by changes in temperature variability

  NEWS COVERAGE: A news release based on this journal publication, which is written for a lay audience and has been approved by an author of the study, is available online: http://bit.ly/lyWhTB

  Citation × Citation Citation Abstract Copy Title: Amplification and dampening of soil respiration by changes in temperature variability Author: Loescher, H. W., Thomann, E., Sierra, C. A., Harmon, M. E., Perakis, S. S. NEWS COVERAGE: A news release based on this journal publication, which is written for a lay audience and has been approved by an author of the study, is available online: http://bit.ly/lyWhTB Title: Amplification and dampening of soil respiration by changes in temperature variability Author: Loescher, H. W., Thomann, E., Sierra, C. A., Harmon, M. E., Perakis, S. S. NEWS COVERAGE: A news release based on this journal publication, which is written for a lay audience and has been approved by an author of the study, is available online: http://bit.ly/lyWhTB Close

• 44. [Article] The effects of elevated temperature and stress on immune function in juvenile chinook salmon (Oncorhynchus tshawytscha)

  Stress, including extreme or rapidly changing temperatures, are known to have deleterious effects on fish health and physiology. This thesis examines the combined effects of elevated acclimation temperature ...

  Citation × Citation Citation Abstract Copy Title: The effects of elevated temperature and stress on immune function in juvenile chinook salmon (Oncorhynchus tshawytscha) Author: Harrahy, Laura Nicole Martini Stress, including extreme or rapidly changing temperatures, are known to have deleterious effects on fish health and physiology. This thesis examines the combined effects of elevated acclimation temperature and acute handling stress on the number of antibody producing cells, plasma lysozyme concentrations, and the number of pronephric leukocytes in juvenile chinook salmon (Oncorhynchus tshawytscha). An additional goal of this thesis was to explore the effects of a temperature fluctuation, as a potential instigator of thermal shock, on innate immunity in wild fall chinook salmon of the Columbia River, specifically to determine if there are effects on plasma lysozyme concentrations and on the frequencies of lymphocytes, neutrophils, and thrombocytes in circulation. Finally, based on results found in an experiment involving elevated acclimation temperature, the relationship between the number of antibody producing cells and fish body weight was examined. Plasma lysozyme concentrations and the number of pronephric leukocytes were both affected by acclimation to 21°C compared to 13°C. While a positive relationship was found between temperature and lysozyme, an inverse relationship was found between temperature and the number of pronephric leukocytes. Plasma lysozyme concentrations, the number of pronephric leukocytes, and the number of antibody producing cells did not respond to the stressor, and the combination of elevated temperature and stress did not have an additive effect on any of the physiological or immunological variables studied. Differences between controls and temperature-treated fish were not detected among individual time points throughout a temperature fluctuation experiment, despite overall responses in plasma lysozyme concentrations and the frequencies of circulating lymphocytes. The frequencies of circulating neutrophils and thrombocytes did not respond to the thermal stressor. Finally, a significant positive relationship was detected between the number of antibody producing cells (assessed by a hemolytic plaque assay) and body weight among non-stressed fish acclimated to 21°C and 13°C. Regardless of acclimation temperature, these results emphasize the importance of the standardization of fish size for immunological experiments. Results from this thesis suggest that some components of innate immunity are affected by elevated acclimation temperatures and that the adaptive immune system is affected by acclimation temperature differently in small and large fish. Title: The effects of elevated temperature and stress on immune function in juvenile chinook salmon (Oncorhynchus tshawytscha) Author: Harrahy, Laura Nicole Martini Stress, including extreme or rapidly changing temperatures, are known to have deleterious effects on fish health and physiology. This thesis examines the combined effects of elevated acclimation temperature and acute handling stress on the number of antibody producing cells, plasma lysozyme concentrations, and the number of pronephric leukocytes in juvenile chinook salmon (Oncorhynchus tshawytscha). An additional goal of this thesis was to explore the effects of a temperature fluctuation, as a potential instigator of thermal shock, on innate immunity in wild fall chinook salmon of the Columbia River, specifically to determine if there are effects on plasma lysozyme concentrations and on the frequencies of lymphocytes, neutrophils, and thrombocytes in circulation. Finally, based on results found in an experiment involving elevated acclimation temperature, the relationship between the number of antibody producing cells and fish body weight was examined. Plasma lysozyme concentrations and the number of pronephric leukocytes were both affected by acclimation to 21°C compared to 13°C. While a positive relationship was found between temperature and lysozyme, an inverse relationship was found between temperature and the number of pronephric leukocytes. Plasma lysozyme concentrations, the number of pronephric leukocytes, and the number of antibody producing cells did not respond to the stressor, and the combination of elevated temperature and stress did not have an additive effect on any of the physiological or immunological variables studied. Differences between controls and temperature-treated fish were not detected among individual time points throughout a temperature fluctuation experiment, despite overall responses in plasma lysozyme concentrations and the frequencies of circulating lymphocytes. The frequencies of circulating neutrophils and thrombocytes did not respond to the thermal stressor. Finally, a significant positive relationship was detected between the number of antibody producing cells (assessed by a hemolytic plaque assay) and body weight among non-stressed fish acclimated to 21°C and 13°C. Regardless of acclimation temperature, these results emphasize the importance of the standardization of fish size for immunological experiments. Results from this thesis suggest that some components of innate immunity are affected by elevated acclimation temperatures and that the adaptive immune system is affected by acclimation temperature differently in small and large fish. Close

• 45. [Article] Repeat temperature measurements in borehole GC-1, northwestern Utah: towards isolating a climate-change signal borehole temperature profiles

  Copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Repeat temperature measurements in borehole GC-1, northwestern Utah: towards isolating a climate-change signal borehole temperature profiles Author: Chapman, David S., Harris, Robert N. Copyrighted by American Geophysical Union Title: Repeat temperature measurements in borehole GC-1, northwestern Utah: towards isolating a climate-change signal borehole temperature profiles Author: Chapman, David S., Harris, Robert N. Copyrighted by American Geophysical Union Close

• 46. [Article] Design of an apparatus with controlled rates of temperature change for use in cold tolerance tests of conifers

  An apparatus was designed to permit freezing tests of needles and other tissue parts from coniferous trees under controlled rates of temperature change with time. The design is based on the principle of ...

  Citation × Citation Citation Abstract Copy Title: Design of an apparatus with controlled rates of temperature change for use in cold tolerance tests of conifers Author: Wessell, William James An apparatus was designed to permit freezing tests of needles and other tissue parts from coniferous trees under controlled rates of temperature change with time. The design is based on the principle of a balanced system of refrigeration demand and heat input to achieve a steady temperature state. The apparatus permits the operator to decrease temperatures from 0°C to -40°C at rates of 1, 2, 3, or 4°C per hour, to hold temperatures at the desired freezing level from 1 to 24 hours, and to increase to 0°C at rates of 1, 2, 3, or 4°C per hour. Temperatures achieved within the sample tubes are accurate to within ± 0. 9°C of the expected temperature. Title: Design of an apparatus with controlled rates of temperature change for use in cold tolerance tests of conifers Author: Wessell, William James An apparatus was designed to permit freezing tests of needles and other tissue parts from coniferous trees under controlled rates of temperature change with time. The design is based on the principle of a balanced system of refrigeration demand and heat input to achieve a steady temperature state. The apparatus permits the operator to decrease temperatures from 0°C to -40°C at rates of 1, 2, 3, or 4°C per hour, to hold temperatures at the desired freezing level from 1 to 24 hours, and to increase to 0°C at rates of 1, 2, 3, or 4°C per hour. Temperatures achieved within the sample tubes are accurate to within ± 0. 9°C of the expected temperature. Close

• 47. [Article] Bridging environmental physiology and community ecology : temperature effects at the community level

  Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how ...

  Citation × Citation Citation Abstract Copy Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Title: Bridging environmental physiology and community ecology : temperature effects at the community level Author: Iles, Alison C. Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. Close

• 48. [Article] Selection and performance evaluation of a test method to assess thermal cracking resistance of asphalt-aggregate mixtures

  Thermal distress in asphalt concrete pavements is a widespread problem around the world. Thermal cracking can be divided into two modes of distress: low temperature cracking and thermal fatigue cracking. ...

  Citation × Citation Citation Abstract Copy Title: Selection and performance evaluation of a test method to assess thermal cracking resistance of asphalt-aggregate mixtures Author: Jung, Duhwoe Thermal distress in asphalt concrete pavements is a widespread problem around the world. Thermal cracking can be divided into two modes of distress: low temperature cracking and thermal fatigue cracking. Low temperature cracking results from extremely cold temperatures; thermal fatigue cracking results from daily temperature cycles. Low temperature cracking is attributed to tensile stresses induced in the asphalt concrete pavement as the temperature drops to an extremely low temperature. If the pavement is cooled, tensile stresses develop as a result of the pavement's tendency to contract. The friction between the pavement and the base layer resists the contraction. If the tensile stress equals the strength of the mixture at that temperature, a micro-crack develops at the surface of the pavement. Under repeated temperature cycles, the crack penetrates the full depth and across the asphalt concrete layer. The thermal stress restrained specimen test (TSRST) was identified as an accelerated laboratory test to evaluate the thermal cracking resistance of asphalt concrete mixtures. The TSRST system developed at OSU includes a load system, data control/acquisition system and software, temperature control system, and specimen alignment stand. The overall system is controlled by a personal computer. A TSRST is conducted by cooling an asphalt concrete specimen at a specified rate while monitoring the specimen at constant length. A typical thermally-induced stress curve is divided into two parts: relaxation and non-relaxation. The temperature at which the curve is divided into two parts is termed the transition temperature. The temperature at fracture is termed the fracture temperature and the maximum stress is the fracture strength. An extensive number of TSRSTs over a wide range of conditions were performed to investigate the thermal cracking resistance of asphalt concrete mixtures. The TSRST results provided a very strong indication of low temperature cracking resistance for all mixtures considered. A ranking of mixtures for low temperature cracking resistance based on the TSRST fracture temperature was in excellent agreement with a ranking based on the physical properties of the asphalt cements. It is highly recommended that the TSRST be used in mix evaluation to identify low temperature cracking resistance of asphalt concrete mixtures. The TSRST showed very promising results regarding the effect of all variables which are currently considered to affect the low temperature cracking of mixtures. The variables considered to have significant affect on the low temperature cracking resistance of mixtures in this study include asphalt type, aggregate type, degree of aging, cooling rate, and stress relaxation. Title: Selection and performance evaluation of a test method to assess thermal cracking resistance of asphalt-aggregate mixtures Author: Jung, Duhwoe Thermal distress in asphalt concrete pavements is a widespread problem around the world. Thermal cracking can be divided into two modes of distress: low temperature cracking and thermal fatigue cracking. Low temperature cracking results from extremely cold temperatures; thermal fatigue cracking results from daily temperature cycles. Low temperature cracking is attributed to tensile stresses induced in the asphalt concrete pavement as the temperature drops to an extremely low temperature. If the pavement is cooled, tensile stresses develop as a result of the pavement's tendency to contract. The friction between the pavement and the base layer resists the contraction. If the tensile stress equals the strength of the mixture at that temperature, a micro-crack develops at the surface of the pavement. Under repeated temperature cycles, the crack penetrates the full depth and across the asphalt concrete layer. The thermal stress restrained specimen test (TSRST) was identified as an accelerated laboratory test to evaluate the thermal cracking resistance of asphalt concrete mixtures. The TSRST system developed at OSU includes a load system, data control/acquisition system and software, temperature control system, and specimen alignment stand. The overall system is controlled by a personal computer. A TSRST is conducted by cooling an asphalt concrete specimen at a specified rate while monitoring the specimen at constant length. A typical thermally-induced stress curve is divided into two parts: relaxation and non-relaxation. The temperature at which the curve is divided into two parts is termed the transition temperature. The temperature at fracture is termed the fracture temperature and the maximum stress is the fracture strength. An extensive number of TSRSTs over a wide range of conditions were performed to investigate the thermal cracking resistance of asphalt concrete mixtures. The TSRST results provided a very strong indication of low temperature cracking resistance for all mixtures considered. A ranking of mixtures for low temperature cracking resistance based on the TSRST fracture temperature was in excellent agreement with a ranking based on the physical properties of the asphalt cements. It is highly recommended that the TSRST be used in mix evaluation to identify low temperature cracking resistance of asphalt concrete mixtures. The TSRST showed very promising results regarding the effect of all variables which are currently considered to affect the low temperature cracking of mixtures. The variables considered to have significant affect on the low temperature cracking resistance of mixtures in this study include asphalt type, aggregate type, degree of aging, cooling rate, and stress relaxation. Close

• 49. [Article] Development of a binary mixture gas composition instrument for use in a confined high temperature environment

  With recent advancements in material science, industrial operations are being conducted at higher and higher temperatures. This is apparent in the nuclear industry where a division of the field is working ...

  Citation × Citation Citation Abstract Copy Title: Development of a binary mixture gas composition instrument for use in a confined high temperature environment Author: Cadell, Seth R. With recent advancements in material science, industrial operations are being conducted at higher and higher temperatures. This is apparent in the nuclear industry where a division of the field is working to develop the High Temperature Gas Reactor and the Very High Temperature Gas Reactor concurrently. Both of these facilities will have outlet gas temperatures that are at significantly higher temperatures than the typical water cooled reactor. These increased temperatures provide improved efficiency for the production of hydrogen, provide direct heating for oil refineries, or more efficient electricity generation. As high temperature operations are being developed, instruments capable of measuring the operating parameters must be developed concurrently. Within the gas reactor community there is a need to measure the impurities within the primary coolant. Current devices will not survive the temperature and radiation environments of a nuclear reactor. An instrument is needed to measure the impurities within the coolant while living inside the reactor, where this instrument would measure the amount of the impurity within the coolant. There are many industrial applications that need to measure the ratio of two components, whether it be the amount of particulate in air that is typical to pneumatic pumping, or the liquid to gas ratio in natural gas as it flows through a pipeline. All of the measurements in these applications can be met using a capacitance sensor. Current capacitance sensors are built to operate at ambient temperatures with only one company producing a product that will handle a temperature of up to 400 °C. This maximum operating temperature is much too low to measure the gas characteristics in the High Temperature Gas Reactor. If this measurement technique were to be improved to operate at the expected temperatures, the coolant within the primary loop could be monitored for water leaks in the steam generator, carbon dust buildup entrained in the flow, or used to measure the purity of the coolant itself. This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core. Title: Development of a binary mixture gas composition instrument for use in a confined high temperature environment Author: Cadell, Seth R. With recent advancements in material science, industrial operations are being conducted at higher and higher temperatures. This is apparent in the nuclear industry where a division of the field is working to develop the High Temperature Gas Reactor and the Very High Temperature Gas Reactor concurrently. Both of these facilities will have outlet gas temperatures that are at significantly higher temperatures than the typical water cooled reactor. These increased temperatures provide improved efficiency for the production of hydrogen, provide direct heating for oil refineries, or more efficient electricity generation. As high temperature operations are being developed, instruments capable of measuring the operating parameters must be developed concurrently. Within the gas reactor community there is a need to measure the impurities within the primary coolant. Current devices will not survive the temperature and radiation environments of a nuclear reactor. An instrument is needed to measure the impurities within the coolant while living inside the reactor, where this instrument would measure the amount of the impurity within the coolant. There are many industrial applications that need to measure the ratio of two components, whether it be the amount of particulate in air that is typical to pneumatic pumping, or the liquid to gas ratio in natural gas as it flows through a pipeline. All of the measurements in these applications can be met using a capacitance sensor. Current capacitance sensors are built to operate at ambient temperatures with only one company producing a product that will handle a temperature of up to 400 °C. This maximum operating temperature is much too low to measure the gas characteristics in the High Temperature Gas Reactor. If this measurement technique were to be improved to operate at the expected temperatures, the coolant within the primary loop could be monitored for water leaks in the steam generator, carbon dust buildup entrained in the flow, or used to measure the purity of the coolant itself. This work details the efforts conducted to develop such an instrument. While the concept of designing a capacitance sensor to measure a gas mixture is not unique, the application of using a capacitance sensor within a nuclear reactor is a new application. This application requires the development of an instrument that will survive a high temperature nuclear reactor environment and operate at a sensitivity not found in current applications. To prove this technique, instrument prototypes were built and tested in confined environments and at high temperatures. This work discusses the proof of concept testing and outlines an application in the High Temperature Test Facility to increase the operational understanding of the instrument. This work is the first step toward the ultimate outcome of this work, which is to provide a new tool to the gas reactor community allowing real-time measurements of coolant properties within the core. Close

• 50. [Article] Borehole temperatures and tree rings: Seasonality and estimates of extratropical Northern Hemispheric warming

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Borehole temperatures and tree rings: Seasonality and estimates of extratropical Northern Hemispheric warming Author: Chapman, David S., Harris, Robert N. Copyrighted by American Geophysical Union. Title: Borehole temperatures and tree rings: Seasonality and estimates of extratropical Northern Hemispheric warming Author: Chapman, David S., Harris, Robert N. Copyrighted by American Geophysical Union. Close