Search

Search Results

• 2151. [Article] Instability and temperature-dependence assessment of IGZO TFTs

  Amorphous oxide semiconductors (AOSs) are of great current interest for thin-film transistor (TFT) channel layer applications. In particular, indium gallium zinc oxide (IGZO) is under intense development ...

  Citation × Citation Citation Abstract Copy Title: Instability and temperature-dependence assessment of IGZO TFTs Author: Hoshino, Ken Amorphous oxide semiconductors (AOSs) are of great current interest for thin-film transistor (TFT) channel layer applications. In particular, indium gallium zinc oxide (IGZO) is under intense development for commercial applications because of its demonstrated high performance at low processing temperatures. The objective of the research presented in this thesis is to provide detailed assessments of device stability, temperature dependence, and related phenomena for IGZO-based TFTs processed at temperatures between 200 °C and 300 °C. TFTs tested exhibit an almost rigid shift in log₁₀(I[subscript D]) – V[subscript GS] transfer curves in which the turn-on voltage, V[subscript ON], moves to a more positive gate voltage with increasing stress time during constant-voltage bias-stress testing of IGZO TFTs. TFT stability is improved as the post-deposition annealing temperature increases over the temperature range of 200 – 300 ºC. The turn-on voltage shift induced by constant-voltage bias-stressing is at least partially reversible; V[subscript ON] tends to recover towards its initial value of V[subscript ON] if the TFT is left unbiased in the dark for a prolonged period of time and better recovery is observed for a longer recovery period. V[subscript ON] for a TFT can be set equal to zero after bias-stress testing if the TFT electrodes are grounded and the TFT is maintained in the dark for a prolonged period of time. Attempts to accelerate the recovery process by application of a negative gate bias at elevated temperature (i.e., 100 ºC) were unsuccessful, resulting in severely degraded subthreshold swing. An almost rigid log₁₀(I[subscript D]) – V[subscript GS] transfer curve shift to a lower (more negative) V[subscript ON] with increasing temperature is observed in the range of –50 °C to +50 °C, except for a TFT with an initial V[subscript ON] equal to zero, in which case the log₁₀(ID) – V[subscript GS] transfer curve is temperature-independent. A more detailed temperature-dependence assessment, however, indicates that the log₁₀(I[subscript D]) – V[subscript GS] transfer curve shift is not exactly rigid since the mobility is found to increase slightly with increasing temperature. A noticeable anomaly is observed in certain log₁₀(I[subscript D]) – VGS transfer curves, especially when obtained at elevated temperature (e.g., 30 and 50 ºC), in which I[subscript D] decreases precipitously near zero volts in the positive gate voltage sweep. This anomaly is attributed to a gate-voltage-step-involved detrapping and subsequent retrapping of electrons in the accumulation channel and/or channel/gate insulator interface. In fact, all IGZO TFT stability and temperature-dependence trends are attributed to channel interface and/or channel bulk trapping/detrapping. Title: Instability and temperature-dependence assessment of IGZO TFTs Author: Hoshino, Ken Amorphous oxide semiconductors (AOSs) are of great current interest for thin-film transistor (TFT) channel layer applications. In particular, indium gallium zinc oxide (IGZO) is under intense development for commercial applications because of its demonstrated high performance at low processing temperatures. The objective of the research presented in this thesis is to provide detailed assessments of device stability, temperature dependence, and related phenomena for IGZO-based TFTs processed at temperatures between 200 °C and 300 °C. TFTs tested exhibit an almost rigid shift in log₁₀(I[subscript D]) – V[subscript GS] transfer curves in which the turn-on voltage, V[subscript ON], moves to a more positive gate voltage with increasing stress time during constant-voltage bias-stress testing of IGZO TFTs. TFT stability is improved as the post-deposition annealing temperature increases over the temperature range of 200 – 300 ºC. The turn-on voltage shift induced by constant-voltage bias-stressing is at least partially reversible; V[subscript ON] tends to recover towards its initial value of V[subscript ON] if the TFT is left unbiased in the dark for a prolonged period of time and better recovery is observed for a longer recovery period. V[subscript ON] for a TFT can be set equal to zero after bias-stress testing if the TFT electrodes are grounded and the TFT is maintained in the dark for a prolonged period of time. Attempts to accelerate the recovery process by application of a negative gate bias at elevated temperature (i.e., 100 ºC) were unsuccessful, resulting in severely degraded subthreshold swing. An almost rigid log₁₀(I[subscript D]) – V[subscript GS] transfer curve shift to a lower (more negative) V[subscript ON] with increasing temperature is observed in the range of –50 °C to +50 °C, except for a TFT with an initial V[subscript ON] equal to zero, in which case the log₁₀(ID) – V[subscript GS] transfer curve is temperature-independent. A more detailed temperature-dependence assessment, however, indicates that the log₁₀(I[subscript D]) – V[subscript GS] transfer curve shift is not exactly rigid since the mobility is found to increase slightly with increasing temperature. A noticeable anomaly is observed in certain log₁₀(I[subscript D]) – VGS transfer curves, especially when obtained at elevated temperature (e.g., 30 and 50 ºC), in which I[subscript D] decreases precipitously near zero volts in the positive gate voltage sweep. This anomaly is attributed to a gate-voltage-step-involved detrapping and subsequent retrapping of electrons in the accumulation channel and/or channel/gate insulator interface. In fact, all IGZO TFT stability and temperature-dependence trends are attributed to channel interface and/or channel bulk trapping/detrapping. Close

• 2152. [Article] Survival and some physiological aspects of tissue cultured cells from Douglas-fir (Pseudotsuga menziesii Mirb. (Franco)) and a poplar hybrid after freezing to liquid nitrogen temperature

  Cell aggregate size in both Douglas-fir and poplar suspension cultures was reduced by the addition of the chelator compounds EDTA and CDTA at concentrations under 100 ppm. Reduced cell aggregate size increased ...

  Citation × Citation Citation Abstract Copy Title: Survival and some physiological aspects of tissue cultured cells from Douglas-fir (Pseudotsuga menziesii Mirb. (Franco)) and a poplar hybrid after freezing to liquid nitrogen temperature Author: Binder, Wolfgang Dieter Cell aggregate size in both Douglas-fir and poplar suspension cultures was reduced by the addition of the chelator compounds EDTA and CDTA at concentrations under 100 ppm. Reduced cell aggregate size increased growth efficiency of suspension cultures of both species. Cell aggregates 550 j.z. or smaller in size were used in the cryogenic studies. At room temperature, the cryoprotectants dimethyl sulfoxide (DMSO) and glycerol at concentrations above 5% were toxic to cell survival; however when these were washed out with fresh media, the growth rate of both Douglas-fir and poplar suspension cultures was increased. The optimum cryoprotectant concentration was about 1.0%. At concentrations above 5% repeated washing with fresh media did not reduce the cellular cryoprotectant concentration and cellular injury or death may have resulted solely from the presence of cryoprotectants, even in the absence of freezing. Cryoprotectant influences observed were thought to be due to cell membrane changes allowing increased nutrient flow in the case of cell death. Cold conditioning or chilling callus at +4°C allowed higher concentrations of cryoprotectants to be added without killing cells. Suspension cultures showed that Douglas-fir entered the log phase of growth 7 days and poplar 3 days after innoculation. Cells were small and densely cytoplasmic during this time. For both species slow freezing of log-growth-phase cells at 1°C/mm was better than fast freezing; a two-step freezing protocol, cooling first to -40°C and then immersion into liquid nitrogen was successful; cooling to -40°C was more effective than cooling to higher temperatures; and fast thawing to +40°C was more effective than slow thawing in air. The cryoprotectants DMSO, glycerol and sucrose are effective alone and in combination. Most effective was a combination of all three; DMSO 5%/glycerol 1%/sucrose 4% for Douglas-fir and DMSO 5%/glycerol 5%/sucrose 4% for poplar. Douglas-fir and poplar cultures on thawing were tested for viability-by assessing ability to reduce tetrazolium salts and ability to continue growth. Poplar cultures resumed growth after approximately 5 weeks post-thaw culture, whereas for Douglas-fir over 80 days was required. Thawed and recultured poplar callus differentiated into shoots and roots. Cold conditioned callus Of both Douglas-fir and poplar produced high TTC reduction values directly after thawing. Cold conditioned poplar callus frozen without cryoprotectantS or liquid responded better on thawing than when frozen with cryoprotectants in liquid media. Douglas-fir buds obtained from field trees in August or seedlings cold conditioned at +4°C for 8 weeks were frozen under various conditions, but no buds survived the freezing process. The development of techniques for successful freeze preservation requires a detailed empirical examination of; prefreezing culture conditions, physiological state and size of cells, cryoprotectant type and concentration used, freezing rate and temperature frozen to, and thaw rate and post-thaw culture conditions. Title: Survival and some physiological aspects of tissue cultured cells from Douglas-fir (Pseudotsuga menziesii Mirb. (Franco)) and a poplar hybrid after freezing to liquid nitrogen temperature Author: Binder, Wolfgang Dieter Cell aggregate size in both Douglas-fir and poplar suspension cultures was reduced by the addition of the chelator compounds EDTA and CDTA at concentrations under 100 ppm. Reduced cell aggregate size increased growth efficiency of suspension cultures of both species. Cell aggregates 550 j.z. or smaller in size were used in the cryogenic studies. At room temperature, the cryoprotectants dimethyl sulfoxide (DMSO) and glycerol at concentrations above 5% were toxic to cell survival; however when these were washed out with fresh media, the growth rate of both Douglas-fir and poplar suspension cultures was increased. The optimum cryoprotectant concentration was about 1.0%. At concentrations above 5% repeated washing with fresh media did not reduce the cellular cryoprotectant concentration and cellular injury or death may have resulted solely from the presence of cryoprotectants, even in the absence of freezing. Cryoprotectant influences observed were thought to be due to cell membrane changes allowing increased nutrient flow in the case of cell death. Cold conditioning or chilling callus at +4°C allowed higher concentrations of cryoprotectants to be added without killing cells. Suspension cultures showed that Douglas-fir entered the log phase of growth 7 days and poplar 3 days after innoculation. Cells were small and densely cytoplasmic during this time. For both species slow freezing of log-growth-phase cells at 1°C/mm was better than fast freezing; a two-step freezing protocol, cooling first to -40°C and then immersion into liquid nitrogen was successful; cooling to -40°C was more effective than cooling to higher temperatures; and fast thawing to +40°C was more effective than slow thawing in air. The cryoprotectants DMSO, glycerol and sucrose are effective alone and in combination. Most effective was a combination of all three; DMSO 5%/glycerol 1%/sucrose 4% for Douglas-fir and DMSO 5%/glycerol 5%/sucrose 4% for poplar. Douglas-fir and poplar cultures on thawing were tested for viability-by assessing ability to reduce tetrazolium salts and ability to continue growth. Poplar cultures resumed growth after approximately 5 weeks post-thaw culture, whereas for Douglas-fir over 80 days was required. Thawed and recultured poplar callus differentiated into shoots and roots. Cold conditioned callus Of both Douglas-fir and poplar produced high TTC reduction values directly after thawing. Cold conditioned poplar callus frozen without cryoprotectantS or liquid responded better on thawing than when frozen with cryoprotectants in liquid media. Douglas-fir buds obtained from field trees in August or seedlings cold conditioned at +4°C for 8 weeks were frozen under various conditions, but no buds survived the freezing process. The development of techniques for successful freeze preservation requires a detailed empirical examination of; prefreezing culture conditions, physiological state and size of cells, cryoprotectant type and concentration used, freezing rate and temperature frozen to, and thaw rate and post-thaw culture conditions. Close

• 2153. [Article] Aboveground biomass and ecosystem carbon pools in tropical secondary forests growing in six life zones of Costa Rica

  Carbon sequestration in tropical secondary forests growing in all climates must be quantified to understand their potential role in adaptation and mitigation strategies of global climate change. Total ...

  Citation × Citation Citation Abstract Copy Title: Aboveground biomass and ecosystem carbon pools in tropical secondary forests growing in six life zones of Costa Rica Author: Cifuentes Jara, Miguel Carbon sequestration in tropical secondary forests growing in all climates must be quantified to understand their potential role in adaptation and mitigation strategies of global climate change. Total aboveground biomass (TAGB), soil carbon, and total ecosystem carbon (TEC) were measured in 54 secondary forests growing along a broad bioclimatic gradient of 6 life zones, from lowland Dry to Premontane Rain forests in Costa Rica. The potential of regenerating secondary forests to offset carbon losses due to climate change-mediated primary forest degradation into the year 2100 was also determined. TAGB ranged from 12 Mg•ha⁻¹ (5 MgC•ha⁻¹) in a 9-yr Dry forest to 298 Mg•ha⁻¹ (143 MgC•ha⁻¹) in a 60-yr Wet forest. TAGB and carbon were correlated with forest age and the ratio of potential evapotranspiration to precipitation. Secondary forests were predicted to reach TAGB ≥ 90% of that in primary forest in 35 to 126 yrs. Mean soil carbon to 1 m ranged from 127 to 278 Mg•ha⁻¹ in the Dry and Premontane Rain life zones. There was no correlation of soil C pools with age. TEC was as high as 440 Mg•ha⁻¹ in a 40-yr Premontane Rain forest. Maximum rates of TEC sequestration were highest (14 – 33 Mg•ha⁻¹•yr⁻¹) in life zones with intermediate levels of precipitation and lowest (7 and 12 Mg•ha⁻¹•yr⁻¹) in the Dry and Premontane Rain life zones. Secondary forests were predicted to attain ecosystem C levels similar to that of primary forests in 44 – 105 yrs. Based upon simulations of forest growth and the changing land area covered by differing life zones due to climate change, carbon losses from primary forests ranged from < 6 to 65 Tg under two different climate change scenarios for the year 2100. Secondary forests would need to cover 19% of each life zone to offset the larger flux of carbon into the atmosphere. Our modeling did not include additional carbon losses associated with changing disturbance regimes and other climate change responses. Results from this study underscore the value of secondary forests for their potential to sequester carbon across a diversity of tropical climates as a means of climate change mitigation. Title: Aboveground biomass and ecosystem carbon pools in tropical secondary forests growing in six life zones of Costa Rica Author: Cifuentes Jara, Miguel Carbon sequestration in tropical secondary forests growing in all climates must be quantified to understand their potential role in adaptation and mitigation strategies of global climate change. Total aboveground biomass (TAGB), soil carbon, and total ecosystem carbon (TEC) were measured in 54 secondary forests growing along a broad bioclimatic gradient of 6 life zones, from lowland Dry to Premontane Rain forests in Costa Rica. The potential of regenerating secondary forests to offset carbon losses due to climate change-mediated primary forest degradation into the year 2100 was also determined. TAGB ranged from 12 Mg•ha⁻¹ (5 MgC•ha⁻¹) in a 9-yr Dry forest to 298 Mg•ha⁻¹ (143 MgC•ha⁻¹) in a 60-yr Wet forest. TAGB and carbon were correlated with forest age and the ratio of potential evapotranspiration to precipitation. Secondary forests were predicted to reach TAGB ≥ 90% of that in primary forest in 35 to 126 yrs. Mean soil carbon to 1 m ranged from 127 to 278 Mg•ha⁻¹ in the Dry and Premontane Rain life zones. There was no correlation of soil C pools with age. TEC was as high as 440 Mg•ha⁻¹ in a 40-yr Premontane Rain forest. Maximum rates of TEC sequestration were highest (14 – 33 Mg•ha⁻¹•yr⁻¹) in life zones with intermediate levels of precipitation and lowest (7 and 12 Mg•ha⁻¹•yr⁻¹) in the Dry and Premontane Rain life zones. Secondary forests were predicted to attain ecosystem C levels similar to that of primary forests in 44 – 105 yrs. Based upon simulations of forest growth and the changing land area covered by differing life zones due to climate change, carbon losses from primary forests ranged from < 6 to 65 Tg under two different climate change scenarios for the year 2100. Secondary forests would need to cover 19% of each life zone to offset the larger flux of carbon into the atmosphere. Our modeling did not include additional carbon losses associated with changing disturbance regimes and other climate change responses. Results from this study underscore the value of secondary forests for their potential to sequester carbon across a diversity of tropical climates as a means of climate change mitigation. Close

• 2154. [Article] Headwater stream characterization : an energy and physical approach to stream temperature using distributed temperature sensing

  Headwater streams are an integral part of the ecological health of the greater stream network as they provide valuable biological habitat, provide upwards to 95% of total in channel flow, while providing ...

  Citation × Citation Citation Abstract Copy Title: Headwater stream characterization : an energy and physical approach to stream temperature using distributed temperature sensing Author: Roth, Travis R. Headwater streams are an integral part of the ecological health of the greater stream network as they provide valuable biological habitat, provide upwards to 95% of total in channel flow, while providing downstream reaches with important constituents such as sediment and woody debris. Small headwater streams are particularly susceptible to anthropogenic and natural disturbances that affect their runoff production, chemical make-up, and thermal regime. Based on their position in the drainage basin and contribution to stream flow, heat energy transfer within a small mountain stream helps establish the thermal regime of the downstream lower order streams. However, headwater catchment thermal function remains poorly understood. Stream temperature is a manifestation of the environment through which it flows and the mechanisms by which it reaches the stream. Subsurface process controls, such as local soil properties, bedrock topography, and lateral flow discharge play an important role in headwater stream generation. Study outcomes are a result of vigorous field experimental work at the Watershed 07 (WS07) stream at the H.J. Andrews Experimental Forest (HJA) located in the Western Cascades, Oregon. Bedrock Topography was delineated through the use of a dynamic cone penetrometer, local lateral inflow sources were identified and quantified through the application of a salt tracer, and the energy budget was characterized through the use of Distributed Temperature Sensing (DTS) technology. High gradient, low volume streams such as WS07 provide unique challenges for DTS deployment which require extensive post-calibration data analysis. An automated cable submersion identification process was developed and was carried out on the collected temperature data with 32.8 % (379 of 1155) of measured temperature points identified as "in-water". Uncertainty propagation analysis associated with DTS measurement was calculated to be 0.21 °C. Salt tracer application found that 2 localized lateral inflow discharge to the stream accounted for 15% and 16% of total discharge in the upper section of the stream. Downstream lateral inflows exhibited incremental additions to stream discharge on the order of 5%. Stream discharge increased by 1.13 l/s from the upper section to the start of the lower section, an increase of 45%. Substantial lateral inflows provided reduction of stream temperatures in the lower section. Using DTS technology we measured stream temperature as a validation method for a physically based energy balance stream temperature model to characterize energy controls on stream temperature. Analysis of model performance was determined through root mean square error with reported values of 0.38 °C and 0.32 °C for the upper and lower section, respectively. Total energy inputs into the upper and lower sections of the stream were 302 W/m² and 210 W/m². Primary energy balance components were found to be solar radiation, atmospheric longwave radiation, and bed conduction. Solar radiation accounted for 63% of total energy flux into the stream in the upper section and 28% in the lower section. This is primarily a result of the distinct vegetation differences between the two reaches. Atmospheric longwave radiation contributed 27% and 26% of total energy flux in the upper and lower sections, respectively. While bed conduction made up 11% and 24% of the total flux in the upper and lower sections. Title: Headwater stream characterization : an energy and physical approach to stream temperature using distributed temperature sensing Author: Roth, Travis R. Headwater streams are an integral part of the ecological health of the greater stream network as they provide valuable biological habitat, provide upwards to 95% of total in channel flow, while providing downstream reaches with important constituents such as sediment and woody debris. Small headwater streams are particularly susceptible to anthropogenic and natural disturbances that affect their runoff production, chemical make-up, and thermal regime. Based on their position in the drainage basin and contribution to stream flow, heat energy transfer within a small mountain stream helps establish the thermal regime of the downstream lower order streams. However, headwater catchment thermal function remains poorly understood. Stream temperature is a manifestation of the environment through which it flows and the mechanisms by which it reaches the stream. Subsurface process controls, such as local soil properties, bedrock topography, and lateral flow discharge play an important role in headwater stream generation. Study outcomes are a result of vigorous field experimental work at the Watershed 07 (WS07) stream at the H.J. Andrews Experimental Forest (HJA) located in the Western Cascades, Oregon. Bedrock Topography was delineated through the use of a dynamic cone penetrometer, local lateral inflow sources were identified and quantified through the application of a salt tracer, and the energy budget was characterized through the use of Distributed Temperature Sensing (DTS) technology. High gradient, low volume streams such as WS07 provide unique challenges for DTS deployment which require extensive post-calibration data analysis. An automated cable submersion identification process was developed and was carried out on the collected temperature data with 32.8 % (379 of 1155) of measured temperature points identified as "in-water". Uncertainty propagation analysis associated with DTS measurement was calculated to be 0.21 °C. Salt tracer application found that 2 localized lateral inflow discharge to the stream accounted for 15% and 16% of total discharge in the upper section of the stream. Downstream lateral inflows exhibited incremental additions to stream discharge on the order of 5%. Stream discharge increased by 1.13 l/s from the upper section to the start of the lower section, an increase of 45%. Substantial lateral inflows provided reduction of stream temperatures in the lower section. Using DTS technology we measured stream temperature as a validation method for a physically based energy balance stream temperature model to characterize energy controls on stream temperature. Analysis of model performance was determined through root mean square error with reported values of 0.38 °C and 0.32 °C for the upper and lower section, respectively. Total energy inputs into the upper and lower sections of the stream were 302 W/m² and 210 W/m². Primary energy balance components were found to be solar radiation, atmospheric longwave radiation, and bed conduction. Solar radiation accounted for 63% of total energy flux into the stream in the upper section and 28% in the lower section. This is primarily a result of the distinct vegetation differences between the two reaches. Atmospheric longwave radiation contributed 27% and 26% of total energy flux in the upper and lower sections, respectively. While bed conduction made up 11% and 24% of the total flux in the upper and lower sections. Close

• 2155. [Article] Identifying candidate genes associated with cold adaptation in Douglas-fir using DNA microarrays

  In forest trees from temperate and boreal regions, cold acclimation is an important adaptive trait that involves changes in gene expression and physiology. Genecological, quantitative genetic, and QTL ...

  Citation × Citation Citation Abstract Copy Title: Identifying candidate genes associated with cold adaptation in Douglas-fir using DNA microarrays Author: Howe, Dana Kathryn In forest trees from temperate and boreal regions, cold acclimation is an important adaptive trait that involves changes in gene expression and physiology. Genecological, quantitative genetic, and QTL studies have been used to study the genetics of cold acclimation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), but the genes responsible for variation among individuals and populations remain unknown. Douglas-fir seedlings from a low elevation, coastal Oregon population and a high elevation, inland Washington population were grown in a common garden in Corvallis, Oregon, and artificial freeze tests were used to compare their cold hardiness from September, 2004 to May, 2005. Cold hardiness was associated with the timing of bud set and bud flush, and there were large population differences in cold acclimation, deacclimation, and bud phenology. In late October, for example, population differences in percent cold damage (predicted at -7°C) were as large as 58% for needles (OR=62% and WA=3%), 48% for stems (OR=53% and WA=5%), and 43% for buds (OR=43% and WA=0%). A custom oligonucleotide microarray was used to analyze gene expression differences between cold susceptible and cold hardy seedlings from the two populations during acclimation. The microarray was developed from >18,000 ESTs from four Douglas-fir cDNA libraries, including three new libraries specifically targeting the stages of cold acclimation, maximum hardiness, and cold deacclimation. Oligonucleotides designed from loblolly pine and white spruce ESTs were included on the microarray to test whether heterologous hybridizations could be used to study Douglas-fir cold acclimation and other processes. Three hundred forty-three differentially expressed Douglas-fir genes were identified (FDR adjusted p-value ≤ 0.01). Many of these genes had similarities to genes encoding dehydrins, heat shock proteins, pathogenesis-related proteins, and genes associated with ABA, GA, and dormancy. Preliminary results suggest that loblolly pine and white spruce ESTs are useful for identifying genes that are differentially expressed during cold acclimation. These differentially expressed genes are considered cold hardiness candidate genes and will be used in genetic association studies of adaptive traits in Douglas-fir from Oregon and Washington. Title: Identifying candidate genes associated with cold adaptation in Douglas-fir using DNA microarrays Author: Howe, Dana Kathryn In forest trees from temperate and boreal regions, cold acclimation is an important adaptive trait that involves changes in gene expression and physiology. Genecological, quantitative genetic, and QTL studies have been used to study the genetics of cold acclimation in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), but the genes responsible for variation among individuals and populations remain unknown. Douglas-fir seedlings from a low elevation, coastal Oregon population and a high elevation, inland Washington population were grown in a common garden in Corvallis, Oregon, and artificial freeze tests were used to compare their cold hardiness from September, 2004 to May, 2005. Cold hardiness was associated with the timing of bud set and bud flush, and there were large population differences in cold acclimation, deacclimation, and bud phenology. In late October, for example, population differences in percent cold damage (predicted at -7°C) were as large as 58% for needles (OR=62% and WA=3%), 48% for stems (OR=53% and WA=5%), and 43% for buds (OR=43% and WA=0%). A custom oligonucleotide microarray was used to analyze gene expression differences between cold susceptible and cold hardy seedlings from the two populations during acclimation. The microarray was developed from >18,000 ESTs from four Douglas-fir cDNA libraries, including three new libraries specifically targeting the stages of cold acclimation, maximum hardiness, and cold deacclimation. Oligonucleotides designed from loblolly pine and white spruce ESTs were included on the microarray to test whether heterologous hybridizations could be used to study Douglas-fir cold acclimation and other processes. Three hundred forty-three differentially expressed Douglas-fir genes were identified (FDR adjusted p-value ≤ 0.01). Many of these genes had similarities to genes encoding dehydrins, heat shock proteins, pathogenesis-related proteins, and genes associated with ABA, GA, and dormancy. Preliminary results suggest that loblolly pine and white spruce ESTs are useful for identifying genes that are differentially expressed during cold acclimation. These differentially expressed genes are considered cold hardiness candidate genes and will be used in genetic association studies of adaptive traits in Douglas-fir from Oregon and Washington. Close

• 2156. [Article] Tectonic and volcanic structures of the southern flank of Axial Volcano, Juan de Fuca Ridge : results from a SeaMARC I sidescan sonar survey

  A 5km swath-width SeaMARC I sidescan sonar survey, conducted over the zone of overlap between the southern rift zone of Axial Volcano and the northern tip of the Vance spreading segment on the Juan de ...

  Citation × Citation Citation Abstract Copy Title: Tectonic and volcanic structures of the southern flank of Axial Volcano, Juan de Fuca Ridge : results from a SeaMARC I sidescan sonar survey Author: Appelgate, T. Bruce A 5km swath-width SeaMARC I sidescan sonar survey, conducted over the zone of overlap between the southern rift zone of Axial Volcano and the northern tip of the Vance spreading segment on the Juan de Fuca Ridge (between 45°24'N and 45°50'N latitude), was analyzed to locate the present position of the Juan de Fuca spreading axis, and to determine the tectonic and volcanic structure of the seafloor. Sidescan data were processed in concert with the ship's Loran-C navigation to construct navigated, orthorectified mosaics of the sidescan imagery. In order to navigate the sidescan swaths, a simple numerical model was developed to describe the tracking behavior of the towed sidescan vehicle. Successive positions and orientations of the sidescan towfish were estimated, and were used to assign latitude/longitude values to individual sidescan pixels. Navigated sidescan pixels were mapped by computer onto an absolute (latitude/longitude) reference grid, and the resulting sidescan mosaic was compared directly to existing high-resolution SeaBeam bathymetry in order to discriminate the effects of large- and small-scale roughness on the observed backscatter distribution. The Juan de Fuca spreading axis between 45°25'N and 45°39'N is located within the axial valley of the Vance segment. Relative age relationships, based on crosscutting and superposition principles, indicate that the most recent volcanism within the axial valley has occurred along the valley's central ridge, and that the most recent resolvable extension within the axial valley has been concentrated between the central ridge and west valley wall. The Vance segment terminates at 45°39'N, and is not associated with a transform fault. The south rift zone of Axial volcano is a constructional volcanic feature that is not faulted, and a discrete axis of spreading over the south flank of Axial volcano is not resolvable in the sidescan imagery; however, the spreading locus north of 45°39'N is constrained to a zone between 130°06'W and 129°54'W. The lack of a well-defined spreading axis north of 45°39'N indicates that the physical manifestation of the divergent plate boundary has been modified or masked by hotspot volcanic processes associated with Axial volcano such that a definitive locus of spreading is not expressed in the surface morphology. Title: Tectonic and volcanic structures of the southern flank of Axial Volcano, Juan de Fuca Ridge : results from a SeaMARC I sidescan sonar survey Author: Appelgate, T. Bruce A 5km swath-width SeaMARC I sidescan sonar survey, conducted over the zone of overlap between the southern rift zone of Axial Volcano and the northern tip of the Vance spreading segment on the Juan de Fuca Ridge (between 45°24'N and 45°50'N latitude), was analyzed to locate the present position of the Juan de Fuca spreading axis, and to determine the tectonic and volcanic structure of the seafloor. Sidescan data were processed in concert with the ship's Loran-C navigation to construct navigated, orthorectified mosaics of the sidescan imagery. In order to navigate the sidescan swaths, a simple numerical model was developed to describe the tracking behavior of the towed sidescan vehicle. Successive positions and orientations of the sidescan towfish were estimated, and were used to assign latitude/longitude values to individual sidescan pixels. Navigated sidescan pixels were mapped by computer onto an absolute (latitude/longitude) reference grid, and the resulting sidescan mosaic was compared directly to existing high-resolution SeaBeam bathymetry in order to discriminate the effects of large- and small-scale roughness on the observed backscatter distribution. The Juan de Fuca spreading axis between 45°25'N and 45°39'N is located within the axial valley of the Vance segment. Relative age relationships, based on crosscutting and superposition principles, indicate that the most recent volcanism within the axial valley has occurred along the valley's central ridge, and that the most recent resolvable extension within the axial valley has been concentrated between the central ridge and west valley wall. The Vance segment terminates at 45°39'N, and is not associated with a transform fault. The south rift zone of Axial volcano is a constructional volcanic feature that is not faulted, and a discrete axis of spreading over the south flank of Axial volcano is not resolvable in the sidescan imagery; however, the spreading locus north of 45°39'N is constrained to a zone between 130°06'W and 129°54'W. The lack of a well-defined spreading axis north of 45°39'N indicates that the physical manifestation of the divergent plate boundary has been modified or masked by hotspot volcanic processes associated with Axial volcano such that a definitive locus of spreading is not expressed in the surface morphology. Close

• 2157. [Article] Beginning the year in a fifth-grade reform-based mathematics classroom : a case study of the development of norms

  The purpose of this qualitative case study was to investigate the development of social norms in a fifth-grade reform-based mathematics classroom through a close examination of one teacher's actions during ...

  Citation × Citation Citation Abstract Copy Title: Beginning the year in a fifth-grade reform-based mathematics classroom : a case study of the development of norms Author: Cheval, Kathryn Meador The purpose of this qualitative case study was to investigate the development of social norms in a fifth-grade reform-based mathematics classroom through a close examination of one teacher's actions during the first three weeks of school. This study offers insights into the following research questions: 1) How does an elementary teacher in a reform-based mathematics classroom negotiate the development of social norms through the context of mathematics at the beginning of the school year? 2) What is the role of social norms in the development of sociomathematical norms? 3) In what ways do teacher moves support or hinder the development of sociomathematical norms? The main data sources were videotaped classroom observations and teacher interviews. Data analysis involved a two-cycle coding process utilizing several coding strategies. The work of Kazemi and Stipek (2001) was used in conceptualizing the categories of social norms found in the data. The findings describe the context of the classroom; the teacher's beliefs, values, and attitudes towards mathematics; and how the teacher set the stage for learning mathematics. There were four specific social norms found in the data that had the potential to become building blocks for sociomathematical norms: 1) students collaborate to solve problems, 2) students view mistakes as a natural part of the learning process, 3) students share strategies and explain their thinking, and 4) students solve problems using a variety of strategies and representations. The teacher negotiated the development of social norms through his choice of high-cognitive demand tasks and collaborative grouping structures as well as pedagogical moves that held students accountable and probed their mathematical thinking. This happened in the context of a supportive classroom environment where students were willing to take risks and talk about their mathematical thinking. The teacher's role as a mathematical authority in the classroom, his use of questioning that sometimes diminished students' thinking, and his language that communicated mixed messages regarding the nature of mathematics may have hindered the development of productive sociomathematical norms. This study has implications for preservice and inservice teachers as well as administrators and professional development leaders in the field of mathematics education. Title: Beginning the year in a fifth-grade reform-based mathematics classroom : a case study of the development of norms Author: Cheval, Kathryn Meador The purpose of this qualitative case study was to investigate the development of social norms in a fifth-grade reform-based mathematics classroom through a close examination of one teacher's actions during the first three weeks of school. This study offers insights into the following research questions: 1) How does an elementary teacher in a reform-based mathematics classroom negotiate the development of social norms through the context of mathematics at the beginning of the school year? 2) What is the role of social norms in the development of sociomathematical norms? 3) In what ways do teacher moves support or hinder the development of sociomathematical norms? The main data sources were videotaped classroom observations and teacher interviews. Data analysis involved a two-cycle coding process utilizing several coding strategies. The work of Kazemi and Stipek (2001) was used in conceptualizing the categories of social norms found in the data. The findings describe the context of the classroom; the teacher's beliefs, values, and attitudes towards mathematics; and how the teacher set the stage for learning mathematics. There were four specific social norms found in the data that had the potential to become building blocks for sociomathematical norms: 1) students collaborate to solve problems, 2) students view mistakes as a natural part of the learning process, 3) students share strategies and explain their thinking, and 4) students solve problems using a variety of strategies and representations. The teacher negotiated the development of social norms through his choice of high-cognitive demand tasks and collaborative grouping structures as well as pedagogical moves that held students accountable and probed their mathematical thinking. This happened in the context of a supportive classroom environment where students were willing to take risks and talk about their mathematical thinking. The teacher's role as a mathematical authority in the classroom, his use of questioning that sometimes diminished students' thinking, and his language that communicated mixed messages regarding the nature of mathematics may have hindered the development of productive sociomathematical norms. This study has implications for preservice and inservice teachers as well as administrators and professional development leaders in the field of mathematics education. Close

• 2158. [Article] Lean thinking in the secondary wood products industry : challenges and benefits

  Due to growing global competition, especially in the last decade, the United States wood and wood-based industries have suffered significant market share losses. The wood industry in Germany is facing ...

  Citation × Citation Citation Abstract Copy Title: Lean thinking in the secondary wood products industry : challenges and benefits Author: Czabke, Jochen Due to growing global competition, especially in the last decade, the United States wood and wood-based industries have suffered significant market share losses. The wood industry in Germany is facing similar challenges. To stay competitive in an increasingly global marketplace, many wood manufacturers are adopting new management/manufacturing approaches. Lean manufacturing is a widely accepted and adopted approach across industries. Lean thinking captures the holistic management approach behind the lean manufacturing terminology. The ultimate goal of a lean organization is to create a smooth, high quality organization that is able to produce finished products at the rate of customer demand in the quality looked-for with slight or no waste. This study documents cases of lean implementation in the United States and German secondary wood products industries. Two “lean leader” companies from each country were studied to identify the successes, failures, and challenges to implementation. Qualitative and quantitative measures were used to document and compare the individual case studies. An embedded multiple-case design approach was applied. Findings of the study, and previous work suggested, that lean thinking can make companies in the secondary wood products industry more profitable. The implementation of lean thinking resulted in more efficient and cost effective manufacturing. Particularly, case companies were able to reduce defects, inventory, and lead time. The study also showed, that if lean thinking was applied to marketing processes, benefits especially in the areas of customer service, new product development, and customer satisfaction were created. The positive results of lean thinking are not limited to those mentioned above, but these were the most common benefits. Case companies were able to realize many other positive effects by implementing lean practices and principles. The key challenges case companies faced during lean implementation were communication issues. All case companies saw it as critical to communicate the new vision and values to all employees. It was seen as extremely important to have everybody understand and accept what lean thinking means and what benefits it can bring to an organization. At the same time this was the main challenge all case companies had to overcome. Title: Lean thinking in the secondary wood products industry : challenges and benefits Author: Czabke, Jochen Due to growing global competition, especially in the last decade, the United States wood and wood-based industries have suffered significant market share losses. The wood industry in Germany is facing similar challenges. To stay competitive in an increasingly global marketplace, many wood manufacturers are adopting new management/manufacturing approaches. Lean manufacturing is a widely accepted and adopted approach across industries. Lean thinking captures the holistic management approach behind the lean manufacturing terminology. The ultimate goal of a lean organization is to create a smooth, high quality organization that is able to produce finished products at the rate of customer demand in the quality looked-for with slight or no waste. This study documents cases of lean implementation in the United States and German secondary wood products industries. Two “lean leader” companies from each country were studied to identify the successes, failures, and challenges to implementation. Qualitative and quantitative measures were used to document and compare the individual case studies. An embedded multiple-case design approach was applied. Findings of the study, and previous work suggested, that lean thinking can make companies in the secondary wood products industry more profitable. The implementation of lean thinking resulted in more efficient and cost effective manufacturing. Particularly, case companies were able to reduce defects, inventory, and lead time. The study also showed, that if lean thinking was applied to marketing processes, benefits especially in the areas of customer service, new product development, and customer satisfaction were created. The positive results of lean thinking are not limited to those mentioned above, but these were the most common benefits. Case companies were able to realize many other positive effects by implementing lean practices and principles. The key challenges case companies faced during lean implementation were communication issues. All case companies saw it as critical to communicate the new vision and values to all employees. It was seen as extremely important to have everybody understand and accept what lean thinking means and what benefits it can bring to an organization. At the same time this was the main challenge all case companies had to overcome. Close

• 2159. [Article] Numerical simulation of cavitating bubble-laden turbulent flows

  Many engineering devices and propulsion systems suffer from undesirable effects of cavitation; such as degradation in the efficiency of pumps and turbines, generation of noise and vibration on ship propeller, ...

  Citation × Citation Citation Abstract Copy Title: Numerical simulation of cavitating bubble-laden turbulent flows Author: Shams Sobhani, Ehsan Many engineering devices and propulsion systems suffer from undesirable effects of cavitation; such as degradation in the efficiency of pumps and turbines, generation of noise and vibration on ship propeller, increased drag and erosion of propeller blade, etc. In spite of decades of research on this problem, detailed study of cavitation physics is still a technical challenge for the current experimental and numerical approaches. Further development of robust and accurate numerical methods for cavitating flow simulation, is the basis of this research. The main objective of this research is to investigate traveling bubble cavitation in turbulent flows. Variable density Navier-Stokes equations are solved in an unstructured grid finite volume solver. Large Eddy Simulation technique with dynamic Smagorinsky subgrid model is used for turbulence modeling. Bubble cavitation is modeled in a Lagrangian framework with subgrid models for forces acting on bubbles. Bubble size variation is modeled using local flow field hydrodynamic pressure for solving Rayliegh-Plesset equation. An adaptive time stepping method is devised for the efficient solution of this highly non-linear equation. Turbulent flow over an open cavity is reproduced numerically from the experimental work by [Liu and Katz, PoF, 08]. Flow statistics agreed very well to those of experiment. Cavitation inception was studied using two different models: (i) discrete bubble model, and (ii) scalar transport model. Severe cavitation was predicted near on top of the trailing edge for cavitation index of σ < 0.4, in agreement to experiments. Dynamics of inception from both models are in good agreement with experiment. A parametric study is performed to study effect of initial gas nuclei size and cavitation number. Cavitation inception is found to occur on top of the trailing edge, which is in agreement with experiment. Inception happens in different pressure coefficient (C[subscript p]) values expected from the classical inception criterion. A PDF analysis on the bubble distribution shows that the larger bubbles are more susceptible to cavitation. Most of the cavitating bubbles are in the regions of negative C[subscript p]. Title: Numerical simulation of cavitating bubble-laden turbulent flows Author: Shams Sobhani, Ehsan Many engineering devices and propulsion systems suffer from undesirable effects of cavitation; such as degradation in the efficiency of pumps and turbines, generation of noise and vibration on ship propeller, increased drag and erosion of propeller blade, etc. In spite of decades of research on this problem, detailed study of cavitation physics is still a technical challenge for the current experimental and numerical approaches. Further development of robust and accurate numerical methods for cavitating flow simulation, is the basis of this research. The main objective of this research is to investigate traveling bubble cavitation in turbulent flows. Variable density Navier-Stokes equations are solved in an unstructured grid finite volume solver. Large Eddy Simulation technique with dynamic Smagorinsky subgrid model is used for turbulence modeling. Bubble cavitation is modeled in a Lagrangian framework with subgrid models for forces acting on bubbles. Bubble size variation is modeled using local flow field hydrodynamic pressure for solving Rayliegh-Plesset equation. An adaptive time stepping method is devised for the efficient solution of this highly non-linear equation. Turbulent flow over an open cavity is reproduced numerically from the experimental work by [Liu and Katz, PoF, 08]. Flow statistics agreed very well to those of experiment. Cavitation inception was studied using two different models: (i) discrete bubble model, and (ii) scalar transport model. Severe cavitation was predicted near on top of the trailing edge for cavitation index of σ < 0.4, in agreement to experiments. Dynamics of inception from both models are in good agreement with experiment. A parametric study is performed to study effect of initial gas nuclei size and cavitation number. Cavitation inception is found to occur on top of the trailing edge, which is in agreement with experiment. Inception happens in different pressure coefficient (C[subscript p]) values expected from the classical inception criterion. A PDF analysis on the bubble distribution shows that the larger bubbles are more susceptible to cavitation. Most of the cavitating bubbles are in the regions of negative C[subscript p]. Close

• 2160. [Article] Coniothyrium rose canker in Oregon

  An isolate of Coniothyrium obtained from a stem canker on Nocturne rose from the Botany Department Farm, Corvallis, Oregon was studied with respect to morphological and cultural characters, pathogenicity ...

  Citation × Citation Citation Abstract Copy Title: Coniothyrium rose canker in Oregon Author: Intrama, Siriphong An isolate of Coniothyrium obtained from a stem canker on Nocturne rose from the Botany Department Farm, Corvallis, Oregon was studied with respect to morphological and cultural characters, pathogenicity and mineral nutrition. The hyphae of the isolate were smooth, septate and branched. The hyphal cells averaged 16.37 X 3.52 microns. The conidia were produced within black, carbonaceous pycnidia with pseudoparenchymatous walls five to six cells thick. Pycnidia averaged 286 X 256 microns. Conidia were extremely small, unicellular, oval shaped and hyaline, 1orne singly on stalk like projections from the innermost cells of the pycnidial wall. The conidia averaged 4.18 x 2.95 microns. On the basis of conidial character, the isolate was considered as Coniothyrium fuckelii, and synonymous with Coniothyrium rosarum. C. fuckelii gained entrance into the host only through wounds. At first penetration was primarily from cell to cell, in the cortex but later extended to part of the vascular cylinder and the pith. The fungus was intracellular. Incubation period was four to five days. The pathogen rarely entered through pruning wounds and did not infect rose leaves. Disease development occurred at temperatures from 10 to 30° C, the optimum being 25° C. This coincides with the optimum for growth of the fungus in culture, The canker lesions developed more rapidly on young succulent stems than on older canes. Rose varieties differed in susceptibility to infection by C. fuckelii. High levels of nitrogen in unbalanced nutrient solutions had a significant effect on size of lesions produced on inoculated rose stems. Whether the increased severity of infection was the result of an effect on the pathogen or increased succulence of the host tissue was not indicated. The callus which sometimes formed above the canker lesion resulted from proliferation of parenchymatous cells in the lower areas of the cortex but was not directly associated with the Coniothyrium infection. Germinating conidia began to send out a single hyaline germ tube after 18 hours incubation. Five percent sucrose solution proved to be the best medium for germination of conidia. Conidia germinated over a range of pH from 3 to 10 with maximum germination at pH 5. In general, acidity seemed to favor germination. Continuous darkness was more or less inhibitory. Minimum temperature for mycelial growth and for formation of pycnidia on PDA was approximately 5° C, the maximum was approximately 35° C and the optimum was 25° C. Coniothyrium fuckelii utilized fructose and mannose as sources of carbon and ammonium tartrate, casein hydrolysate. and urea as sources of nitrogen. Growth occurred within a pH range f 3.0 to 9.0, with optimum growth at a initial pH of 4.0. Numerous pycnidia were formed in media with initial pH values from 3.0 to 7.0. White light exerted a strong effect on pigment production in themycelium and on pycnidial formation. It also enhanced canker development on the rose canes. Young cultures of the fungus produced both submerged and aerial mycelium that was at first white and fluffy but became buff colored, then light brown as the culture aged. White light caused formation of a dark-green colored mycelium. Title: Coniothyrium rose canker in Oregon Author: Intrama, Siriphong An isolate of Coniothyrium obtained from a stem canker on Nocturne rose from the Botany Department Farm, Corvallis, Oregon was studied with respect to morphological and cultural characters, pathogenicity and mineral nutrition. The hyphae of the isolate were smooth, septate and branched. The hyphal cells averaged 16.37 X 3.52 microns. The conidia were produced within black, carbonaceous pycnidia with pseudoparenchymatous walls five to six cells thick. Pycnidia averaged 286 X 256 microns. Conidia were extremely small, unicellular, oval shaped and hyaline, 1orne singly on stalk like projections from the innermost cells of the pycnidial wall. The conidia averaged 4.18 x 2.95 microns. On the basis of conidial character, the isolate was considered as Coniothyrium fuckelii, and synonymous with Coniothyrium rosarum. C. fuckelii gained entrance into the host only through wounds. At first penetration was primarily from cell to cell, in the cortex but later extended to part of the vascular cylinder and the pith. The fungus was intracellular. Incubation period was four to five days. The pathogen rarely entered through pruning wounds and did not infect rose leaves. Disease development occurred at temperatures from 10 to 30° C, the optimum being 25° C. This coincides with the optimum for growth of the fungus in culture, The canker lesions developed more rapidly on young succulent stems than on older canes. Rose varieties differed in susceptibility to infection by C. fuckelii. High levels of nitrogen in unbalanced nutrient solutions had a significant effect on size of lesions produced on inoculated rose stems. Whether the increased severity of infection was the result of an effect on the pathogen or increased succulence of the host tissue was not indicated. The callus which sometimes formed above the canker lesion resulted from proliferation of parenchymatous cells in the lower areas of the cortex but was not directly associated with the Coniothyrium infection. Germinating conidia began to send out a single hyaline germ tube after 18 hours incubation. Five percent sucrose solution proved to be the best medium for germination of conidia. Conidia germinated over a range of pH from 3 to 10 with maximum germination at pH 5. In general, acidity seemed to favor germination. Continuous darkness was more or less inhibitory. Minimum temperature for mycelial growth and for formation of pycnidia on PDA was approximately 5° C, the maximum was approximately 35° C and the optimum was 25° C. Coniothyrium fuckelii utilized fructose and mannose as sources of carbon and ammonium tartrate, casein hydrolysate. and urea as sources of nitrogen. Growth occurred within a pH range f 3.0 to 9.0, with optimum growth at a initial pH of 4.0. Numerous pycnidia were formed in media with initial pH values from 3.0 to 7.0. White light exerted a strong effect on pigment production in themycelium and on pycnidial formation. It also enhanced canker development on the rose canes. Young cultures of the fungus produced both submerged and aerial mycelium that was at first white and fluffy but became buff colored, then light brown as the culture aged. White light caused formation of a dark-green colored mycelium. Close