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• 401. [Article] Verticillium wilt of hops : pathogenicity, host range, and temperature relations of the causal agents

  Verticillium wilt of hops in Oregon, caused by Verticillium dahliae Kleb., was first reported in 1956. Later, V. albo-atrum Reinke & Berth. was also isolated from infected hop plants, and thus both species ...

  Citation × Citation Citation Abstract Copy Title: Verticillium wilt of hops : pathogenicity, host range, and temperature relations of the causal agents Author: Zehsazian, Hassan Verticillium wilt of hops in Oregon, caused by Verticillium dahliae Kleb., was first reported in 1956. Later, V. albo-atrum Reinke & Berth. was also isolated from infected hop plants, and thus both species of the fungus were shown to be the causal agents of the disease in Oregon. The purpose of this research was to study temperature relations and host range of hop isolates of Verticillium existing in Oregon, and also to determine infectivity and pathogenicity of these isolates to different varieties of hops. The temperature relations of two V. dahliae and two V. alboatrum isolates, recovered from infected hops grown throughout the Willamette Valley of Oregon, were studied by dry weight measurements. Two additional V. dahliae isolates, one from peppermint and one from potato, were included in the experiments, The isolates were grown in Czapek. Dox broth plus yeast extract at ten temperatures between 5° and 32°C. The dry weight was affected by the interactions of isolate, temperature, and period of incubation. At temperatures up to 17°C, the dry weights of all isolates were increased by longer incubation periods with no autolysis of the mycelial mass observed in 17 days. Above 17°, however, the incubation periods required for maximum dry weight production and the onset of autolysis varied, depending on the temperature and the isolate. A faster initial growth rate, caused by increasing temperature, hastened the onset of autolysis, and thus did not result in greater amounts of dry weight production in longer periods. On the other hand, a slow initial growth rate, caused by too high a temperature, resulted in delay of autolysis and production of greater dry weights in longer incubation periods. V. albo-atrum isolates did not grow at 30°C and evidence was obtained showing that failure to grow was due to thermal death of germinated and ungerminated spore inoculum rather than to inhibition of germination. All V. dahliae isolates grew fairly well at 30°C but failed to grow at 32°C. The latter temperature was lethal to the spore inocula of V. dahliae isolates after 7 to 12 days of incubation. These results point out a significant physiological difference between V. albo-atrum and V. dahliae and thus support the validity of considering V. dahliae as a distinct species. In host range studies, one V. albo-atrum isolate (No. 138), originally obtained from Fuggle hops, was found to infect and proliferate greatly in stems of potato, and to a lesser extent in tomato and eggplant. Among V. dahliae isolates, one originally recovered from Bullion hops (No. 148), proliferated poorly in potato, eggplant, and strawberry. The other (No. 150), obtained from Fuggle hops, proliferated greatly in stems of peppermint and was highly pathogenic to that host. The conclusion was reached that the hop isolates of Verticillium existing in Oregon, are primarily pathogens of other plants, with host ranges that include hops to some extent. Verticillium isolates from infected hops, peppermint and potato, infected a low percentage of plants among 14 hop varieties grown in infested soil. Differently prepared inoculum (laboratory infested soils and straw culture) or different levels of inoculum, did not affect the percentage of infected plants appreciably. All Verticillium isolates, regardless of their origin or species, proliferated poorly in stems of infected hop plants and no actual wilting or death of the infected plants was observed. It was concluded that the strains of Verticillium affecting hops in Oregon are not virulent pathogens of this crop and that they are primarily adapted to plants other than hops. Title: Verticillium wilt of hops : pathogenicity, host range, and temperature relations of the causal agents Author: Zehsazian, Hassan Verticillium wilt of hops in Oregon, caused by Verticillium dahliae Kleb., was first reported in 1956. Later, V. albo-atrum Reinke & Berth. was also isolated from infected hop plants, and thus both species of the fungus were shown to be the causal agents of the disease in Oregon. The purpose of this research was to study temperature relations and host range of hop isolates of Verticillium existing in Oregon, and also to determine infectivity and pathogenicity of these isolates to different varieties of hops. The temperature relations of two V. dahliae and two V. alboatrum isolates, recovered from infected hops grown throughout the Willamette Valley of Oregon, were studied by dry weight measurements. Two additional V. dahliae isolates, one from peppermint and one from potato, were included in the experiments, The isolates were grown in Czapek. Dox broth plus yeast extract at ten temperatures between 5° and 32°C. The dry weight was affected by the interactions of isolate, temperature, and period of incubation. At temperatures up to 17°C, the dry weights of all isolates were increased by longer incubation periods with no autolysis of the mycelial mass observed in 17 days. Above 17°, however, the incubation periods required for maximum dry weight production and the onset of autolysis varied, depending on the temperature and the isolate. A faster initial growth rate, caused by increasing temperature, hastened the onset of autolysis, and thus did not result in greater amounts of dry weight production in longer periods. On the other hand, a slow initial growth rate, caused by too high a temperature, resulted in delay of autolysis and production of greater dry weights in longer incubation periods. V. albo-atrum isolates did not grow at 30°C and evidence was obtained showing that failure to grow was due to thermal death of germinated and ungerminated spore inoculum rather than to inhibition of germination. All V. dahliae isolates grew fairly well at 30°C but failed to grow at 32°C. The latter temperature was lethal to the spore inocula of V. dahliae isolates after 7 to 12 days of incubation. These results point out a significant physiological difference between V. albo-atrum and V. dahliae and thus support the validity of considering V. dahliae as a distinct species. In host range studies, one V. albo-atrum isolate (No. 138), originally obtained from Fuggle hops, was found to infect and proliferate greatly in stems of potato, and to a lesser extent in tomato and eggplant. Among V. dahliae isolates, one originally recovered from Bullion hops (No. 148), proliferated poorly in potato, eggplant, and strawberry. The other (No. 150), obtained from Fuggle hops, proliferated greatly in stems of peppermint and was highly pathogenic to that host. The conclusion was reached that the hop isolates of Verticillium existing in Oregon, are primarily pathogens of other plants, with host ranges that include hops to some extent. Verticillium isolates from infected hops, peppermint and potato, infected a low percentage of plants among 14 hop varieties grown in infested soil. Differently prepared inoculum (laboratory infested soils and straw culture) or different levels of inoculum, did not affect the percentage of infected plants appreciably. All Verticillium isolates, regardless of their origin or species, proliferated poorly in stems of infected hop plants and no actual wilting or death of the infected plants was observed. It was concluded that the strains of Verticillium affecting hops in Oregon are not virulent pathogens of this crop and that they are primarily adapted to plants other than hops. Close

• 402. [Article] Perturbed angular correlation investigation of cubic zirconia

  Perturbed angular correlation (PAC) spectra of fully yttria-stabilized (cubic) zirconia with Y₂0₃ contents of 35.4 wt. %, 27.8 wt. %, and 16.9 wt. %, respectively, were measured using the isotope ¹⁸¹Ta ...

  Citation × Citation Citation Abstract Copy Title: Perturbed angular correlation investigation of cubic zirconia Author: Fuchs, Heinz D. Perturbed angular correlation (PAC) spectra of fully yttria-stabilized (cubic) zirconia with Y₂0₃ contents of 35.4 wt. %, 27.8 wt. %, and 16.9 wt. %, respectively, were measured using the isotope ¹⁸¹Ta as probe nucleus. PAC spectra in cubic zirconia are characterized by a wide frequency distribution due to contributions of dopant cations (Y) and oxygen vacancies. The jump rate for oxygen vacancies in the lattice is several orders of magnitude higher than for the cations. In the entire temperature range (24°C to 1300°C) the cations can be considered static, whereas the mobility of the anion vacancies is strongly temperature-dependent. The spectra show that the electric field gradient (EFG) is static at highest (T > 1200°C) and lowest (T < 500°C) temperatures. The contributions to the EFG due to oxygen vacancies average to zero for the highest temperatures because of the fast vacancy jump rate. At the lowest temperatures, the vacancy jump time is greater than the lifetime of the intermediate state (10.8 ns), resulting in a static EFG. A relaxation phenomena arising from diffusion of oxygen vacancies was observed for intermediate temperatures. The relaxation parameter, λ, has a maximum at about 850°C. In the high-temperature region (T > 850°C), λ has an activated form. The activation energy for the oxygen vacancy motion, E[subscript a], is 1.06 eV (± 0.07 eV) and is independent of the Y₂0₃ concentration which contradicts results obtained from ionic conductivity measurements found in the literature. The EFG increases by a factor of three with decreasing temperature from 1200°C to 500°C. It is proposed that this is caused by dynamical screening: at elevated temperatures oxygen vacancies jump into higher-energy positions closer to the PAC probe, reducing the cationic contribution to the EFG. The activation energy for this process is 0.2 eV (± 0.02 eV). PAC measurements on samples heated up to different temperatures show that the material must be annealed for about 24 hours at 1300°C. Even though the Y₂0₃ concentrations were 16.9 wt. % and higher, the samples were inhomogeneous without annealing. A computer simulation of the angular perturbation function, G₂(t), was developed, and the results for a static EFG, the XYZ model, and rapidly jumping vacancies in a simple cubic lattice are presented. The simulation assumes that (i) the atoms of Zr and Y are randomly distributed, (ii) the oxygen vacancies can be described as point ions, (iii) there are no interactions between the oxygen vacancies and no interactions between the vacancies and Zr or Y, (iv) the vacancies can only jump to next-nearest-neighbor sites, and (v) the vacancies never occupy nearest-neighbor sites to the PAC probe. The results from the static EFG and the XYZ model are in agreement with theoretical calculations. The transition probability, W, between two particular EFG states per unit time is proportional to the inverse of the average correlation time, τ[subscript c], and the number of possible EFG states, N. Title: Perturbed angular correlation investigation of cubic zirconia Author: Fuchs, Heinz D. Perturbed angular correlation (PAC) spectra of fully yttria-stabilized (cubic) zirconia with Y₂0₃ contents of 35.4 wt. %, 27.8 wt. %, and 16.9 wt. %, respectively, were measured using the isotope ¹⁸¹Ta as probe nucleus. PAC spectra in cubic zirconia are characterized by a wide frequency distribution due to contributions of dopant cations (Y) and oxygen vacancies. The jump rate for oxygen vacancies in the lattice is several orders of magnitude higher than for the cations. In the entire temperature range (24°C to 1300°C) the cations can be considered static, whereas the mobility of the anion vacancies is strongly temperature-dependent. The spectra show that the electric field gradient (EFG) is static at highest (T > 1200°C) and lowest (T < 500°C) temperatures. The contributions to the EFG due to oxygen vacancies average to zero for the highest temperatures because of the fast vacancy jump rate. At the lowest temperatures, the vacancy jump time is greater than the lifetime of the intermediate state (10.8 ns), resulting in a static EFG. A relaxation phenomena arising from diffusion of oxygen vacancies was observed for intermediate temperatures. The relaxation parameter, λ, has a maximum at about 850°C. In the high-temperature region (T > 850°C), λ has an activated form. The activation energy for the oxygen vacancy motion, E[subscript a], is 1.06 eV (± 0.07 eV) and is independent of the Y₂0₃ concentration which contradicts results obtained from ionic conductivity measurements found in the literature. The EFG increases by a factor of three with decreasing temperature from 1200°C to 500°C. It is proposed that this is caused by dynamical screening: at elevated temperatures oxygen vacancies jump into higher-energy positions closer to the PAC probe, reducing the cationic contribution to the EFG. The activation energy for this process is 0.2 eV (± 0.02 eV). PAC measurements on samples heated up to different temperatures show that the material must be annealed for about 24 hours at 1300°C. Even though the Y₂0₃ concentrations were 16.9 wt. % and higher, the samples were inhomogeneous without annealing. A computer simulation of the angular perturbation function, G₂(t), was developed, and the results for a static EFG, the XYZ model, and rapidly jumping vacancies in a simple cubic lattice are presented. The simulation assumes that (i) the atoms of Zr and Y are randomly distributed, (ii) the oxygen vacancies can be described as point ions, (iii) there are no interactions between the oxygen vacancies and no interactions between the vacancies and Zr or Y, (iv) the vacancies can only jump to next-nearest-neighbor sites, and (v) the vacancies never occupy nearest-neighbor sites to the PAC probe. The results from the static EFG and the XYZ model are in agreement with theoretical calculations. The transition probability, W, between two particular EFG states per unit time is proportional to the inverse of the average correlation time, τ[subscript c], and the number of possible EFG states, N. Close

• 403. [Article] Effect of temperature on seed dormancy and alpha-amylase activity during kernel maturation and germination in wheat (Triticum aestivum L.) cultivars

  Effect of temperature on seed dormancy, alpha-amylase activity and kernel weight in five wheat (Triticum aestivum L.) varieties was studied. Three ripening temperature conditions - 15.5°C, 26.6 °C and ...

  Citation × Citation Citation Abstract Copy Title: Effect of temperature on seed dormancy and alpha-amylase activity during kernel maturation and germination in wheat (Triticum aestivum L.) cultivars Author: Reddy, Lekkala Vijayasimha Effect of temperature on seed dormancy, alpha-amylase activity and kernel weight in five wheat (Triticum aestivum L.) varieties was studied. Three ripening temperature conditions - 15.5°C, 26.6 °C and "Field" were used to induce dormancy. Alpha-amylase activity and kernel weight of developing kernels was determined every ten days after anthesis until maturity. Dormancy in kernels was examined at germination temperatures of 15. 5°C, 20°C and 26. 6°C. Alpha- amylase activity during germination of kernels was determined on 1st, 2nd, 3rd and 6th day. In developing kernels alpha-amylase activity peaked at 10 to 20 days after anthesis and dropped or levelled-off as the kernels approached maturity. This was observed at both 15.5°C and 26.6° C . However, the peak was not obvious at 26.6°C because of the enzyme activity was lower at this temperature than at 15.5°C. In kernels ripened in field, the enzyme activity fluctuated apparently depending upon the changes in weather conditions, especially temperature. A faster growth of kernels and higher final dry kernel weight were noticed at 26.6°C and field temperature conditions than at 15.5°C. Significant varietal differences were observed in both alpha-amylase activity in kernels and kernel weight during the development and maturation of kernels. Kernels of all varieties, ripened at 26.6 °C, germinated as fast as non-dormant check kernels at 15.5°C but exhibited varying degrees of dormancy when germinated at 20 °C and 26.6°C. In contrast, kernels of Brevor, Tom Thumb and P.I. 178211, ripened at 15.5 °C showed a high level of dormancy as shown by their failure to germinate at 20 °C and 26.6 °C, and slow germination at 15.5⁰ C. Kernels of Hyslop and Yamhill, ripened at 15.5°C, did not show dormancy at 15.5°C but showed some dormancy at 20°C and 26.6°C. This dormancy, however, was less than in Brevor, Tom Thumb and P.I. 178211. Field ripened kernels of Yamhill and Hyslpp when germinated at 15.5°C, did not show any dormancy; whereas, P.I. 178211, Brevor and Tom Thumb expressed different degrees of dormancy. Kernels of all varieties, ripened in the field, when germinated at 20°C or 26.6 °C, showed different degrees of dormancy except Yamhill. Yamhill did not differ significantly from the one year old non-dormant check kernels at 26.6° C . A substantial increse in alpha-amylase occurred only in germinated kernels. Although kernels of all varieties ripened at 26.6°C showed about the same weighted germination percentage at 15.5°C, germinated kernels of Yamhill, Hyslop and P.I. 178211 and had highly significant greater alpha-amylase activity than those of Brevor and Tom Thumb. In general, lower alpha-amylase activity was observed at higher germination temperatures. However, the data indicate that the enzyme activity depends to some extent on the ripening temperature conditions. Thus the results indicated that seed dormancy, alpha-amylase activity and kernel weight are determined by the genotype of a variety and influenced by the temperature during maturation and germination of kernels. Title: Effect of temperature on seed dormancy and alpha-amylase activity during kernel maturation and germination in wheat (Triticum aestivum L.) cultivars Author: Reddy, Lekkala Vijayasimha Effect of temperature on seed dormancy, alpha-amylase activity and kernel weight in five wheat (Triticum aestivum L.) varieties was studied. Three ripening temperature conditions - 15.5°C, 26.6 °C and "Field" were used to induce dormancy. Alpha-amylase activity and kernel weight of developing kernels was determined every ten days after anthesis until maturity. Dormancy in kernels was examined at germination temperatures of 15. 5°C, 20°C and 26. 6°C. Alpha- amylase activity during germination of kernels was determined on 1st, 2nd, 3rd and 6th day. In developing kernels alpha-amylase activity peaked at 10 to 20 days after anthesis and dropped or levelled-off as the kernels approached maturity. This was observed at both 15.5°C and 26.6° C . However, the peak was not obvious at 26.6°C because of the enzyme activity was lower at this temperature than at 15.5°C. In kernels ripened in field, the enzyme activity fluctuated apparently depending upon the changes in weather conditions, especially temperature. A faster growth of kernels and higher final dry kernel weight were noticed at 26.6°C and field temperature conditions than at 15.5°C. Significant varietal differences were observed in both alpha-amylase activity in kernels and kernel weight during the development and maturation of kernels. Kernels of all varieties, ripened at 26.6 °C, germinated as fast as non-dormant check kernels at 15.5°C but exhibited varying degrees of dormancy when germinated at 20 °C and 26.6°C. In contrast, kernels of Brevor, Tom Thumb and P.I. 178211, ripened at 15.5 °C showed a high level of dormancy as shown by their failure to germinate at 20 °C and 26.6 °C, and slow germination at 15.5⁰ C. Kernels of Hyslop and Yamhill, ripened at 15.5°C, did not show dormancy at 15.5°C but showed some dormancy at 20°C and 26.6°C. This dormancy, however, was less than in Brevor, Tom Thumb and P.I. 178211. Field ripened kernels of Yamhill and Hyslpp when germinated at 15.5°C, did not show any dormancy; whereas, P.I. 178211, Brevor and Tom Thumb expressed different degrees of dormancy. Kernels of all varieties, ripened in the field, when germinated at 20°C or 26.6 °C, showed different degrees of dormancy except Yamhill. Yamhill did not differ significantly from the one year old non-dormant check kernels at 26.6° C . A substantial increse in alpha-amylase occurred only in germinated kernels. Although kernels of all varieties ripened at 26.6°C showed about the same weighted germination percentage at 15.5°C, germinated kernels of Yamhill, Hyslop and P.I. 178211 and had highly significant greater alpha-amylase activity than those of Brevor and Tom Thumb. In general, lower alpha-amylase activity was observed at higher germination temperatures. However, the data indicate that the enzyme activity depends to some extent on the ripening temperature conditions. Thus the results indicated that seed dormancy, alpha-amylase activity and kernel weight are determined by the genotype of a variety and influenced by the temperature during maturation and germination of kernels. Close

• 404. [Article] Effect of moisture, temperature, and sulfur dioxide on color of dried apples

  When sulfur dioxide is used in commercial drying of fruits in combination with low storage temperatures, browning and microbial spoilage can be inhibited. However, the relationship between moisture level, storage ...

  Citation × Citation Citation Abstract Copy Title: Effect of moisture, temperature, and sulfur dioxide on color of dried apples Author: Sayavedra-Soto, Luis Alberto When sulfur dioxide is used in commercial drying of fruits in combination with low storage temperatures, browning and microbial spoilage can be inhibited. However, the relationship between moisture level, storage temperature, and sulfur dioxide content on the color of dried fruit is not known; therefore the purpose of this research was to determine the influence of temperature, sulfur dioxide content, and moisture level on the color of dried apples during storage. Dices (3/4" x 1/2" x 1/4") of Golden Delicious apples were dried after a 90 sec dip in aqueous solutions of 2500, 5000, or 7500 ppm of sulfur dioxide obtained from sodium bisulfite. The apples were dried to five different levels of moisture (13, 18, 22, 24, and 26% wet basis) and stored in controlled temperature rooms at 1°, 21°, and 38°C. Periodically the samples were analyzed for color (color index (CI) defined as Hunter L x a [subscript L] x b [subscript L]), total and free sulfur dioxide, moisture and water activity (a [subscript w]), to appreciate the changes of quality during 385 days of storage. Sulfur dioxide level was directly influenced by storage temperature. As temperature increased, the sulfur dioxide level in the dried apples decreased following a negative exponential curve. At 1°C nearly no variation in sulfur dioxide level was observed during the experiment. Loss of free sulfur dioxide followed the same pattern as total sulfur dioxide. The concentration of free sulfur dioxide was a larger proportion of the total as the concentration of total sulfur dioxide was increased. Moisture content of the dried apples decreased during storage at 38°C, but at 21°C moisture content decreased in the first 40 days reaching a level that remained constant until the end of the experiment. The constant level was approximately 85% of the initial moisture level. No appreciable change of water content occurred at 1°C. Water activities of the samples ranged between 0.40 and 0.85 and the optimal levels for color retention at the lower concentrations of total sulfur dioxide were approximately 0.75 a [subscript w]. This corresponded to a moisture of approximately 20%. Total sulfur dioxide, moisture and CI analysis of the dried apples were used to derive three equations, one for each temperature of storage. From these equations, the following relationships were evident. CI described the changes in color during the 385 days of the experiment. At 1°C sulfur dioxide and moisture influenced the changes of color approximately the same extent. Moisture content of 20% at all levels of sulfur dioxide at 1°C was optimal for maximum color preservation. Samples stored at 1°C retained an acceptable color longer than those stored at 21°C or 38°C. The approximation of the equation derived from regression analysis of the data of changes in color at 1°C was 63%. Changes in color at 21°C occurred faster than at 1°C. Acceptable colors were found until the 188 day samples. The water content of the samples had more influence on the color changes than the total sulfur dioxide content as determined by the regression equation. The regression equation describes 88% of the variations in color. Concentrations higher than 1500 ppm of total sulfur dioxide were necessary to maintain samples of acceptable colors for periods up to 188 days with moisture levels close to 20%. Storage temperature of 21°C was satisfactory for samples that do not require storage periods longer than 200 days and contain 1500 ppm of total sulfur dioxide and 20% moisture. Very rapid changes in the parameters studied were observed at 38°C. The samples were very dark after 40 days and none had an acceptable color after 101 days of storage. The regression equation derived from the data described 87% of the variations of color. The temperature of 38°C is not recommended under any condition for storage of dried apples. It was concluded that temperatures lower than 21°C and concentrations of approximately 1500 ppm of sulfur dioxide in the fruit tissue could preserve acceptable colors in samples of dried apples for periods of 200 days. Longer storage periods would be possible as temperature approaches 1°C. Using the equations obtained in this experiment, an estimation can be made of the storage life of dried apples. The response surface diagrams obtained are useful for visual comprehension of the influence of temperature, sulfur dioxide and moisture on color throughout the time of storage. Title: Effect of moisture, temperature, and sulfur dioxide on color of dried apples Author: Sayavedra-Soto, Luis Alberto When sulfur dioxide is used in commercial drying of fruits in combination with low storage temperatures, browning and microbial spoilage can be inhibited. However, the relationship between moisture level, storage temperature, and sulfur dioxide content on the color of dried fruit is not known; therefore the purpose of this research was to determine the influence of temperature, sulfur dioxide content, and moisture level on the color of dried apples during storage. Dices (3/4" x 1/2" x 1/4") of Golden Delicious apples were dried after a 90 sec dip in aqueous solutions of 2500, 5000, or 7500 ppm of sulfur dioxide obtained from sodium bisulfite. The apples were dried to five different levels of moisture (13, 18, 22, 24, and 26% wet basis) and stored in controlled temperature rooms at 1°, 21°, and 38°C. Periodically the samples were analyzed for color (color index (CI) defined as Hunter L x a [subscript L] x b [subscript L]), total and free sulfur dioxide, moisture and water activity (a [subscript w]), to appreciate the changes of quality during 385 days of storage. Sulfur dioxide level was directly influenced by storage temperature. As temperature increased, the sulfur dioxide level in the dried apples decreased following a negative exponential curve. At 1°C nearly no variation in sulfur dioxide level was observed during the experiment. Loss of free sulfur dioxide followed the same pattern as total sulfur dioxide. The concentration of free sulfur dioxide was a larger proportion of the total as the concentration of total sulfur dioxide was increased. Moisture content of the dried apples decreased during storage at 38°C, but at 21°C moisture content decreased in the first 40 days reaching a level that remained constant until the end of the experiment. The constant level was approximately 85% of the initial moisture level. No appreciable change of water content occurred at 1°C. Water activities of the samples ranged between 0.40 and 0.85 and the optimal levels for color retention at the lower concentrations of total sulfur dioxide were approximately 0.75 a [subscript w]. This corresponded to a moisture of approximately 20%. Total sulfur dioxide, moisture and CI analysis of the dried apples were used to derive three equations, one for each temperature of storage. From these equations, the following relationships were evident. CI described the changes in color during the 385 days of the experiment. At 1°C sulfur dioxide and moisture influenced the changes of color approximately the same extent. Moisture content of 20% at all levels of sulfur dioxide at 1°C was optimal for maximum color preservation. Samples stored at 1°C retained an acceptable color longer than those stored at 21°C or 38°C. The approximation of the equation derived from regression analysis of the data of changes in color at 1°C was 63%. Changes in color at 21°C occurred faster than at 1°C. Acceptable colors were found until the 188 day samples. The water content of the samples had more influence on the color changes than the total sulfur dioxide content as determined by the regression equation. The regression equation describes 88% of the variations in color. Concentrations higher than 1500 ppm of total sulfur dioxide were necessary to maintain samples of acceptable colors for periods up to 188 days with moisture levels close to 20%. Storage temperature of 21°C was satisfactory for samples that do not require storage periods longer than 200 days and contain 1500 ppm of total sulfur dioxide and 20% moisture. Very rapid changes in the parameters studied were observed at 38°C. The samples were very dark after 40 days and none had an acceptable color after 101 days of storage. The regression equation derived from the data described 87% of the variations of color. The temperature of 38°C is not recommended under any condition for storage of dried apples. It was concluded that temperatures lower than 21°C and concentrations of approximately 1500 ppm of sulfur dioxide in the fruit tissue could preserve acceptable colors in samples of dried apples for periods of 200 days. Longer storage periods would be possible as temperature approaches 1°C. Using the equations obtained in this experiment, an estimation can be made of the storage life of dried apples. The response surface diagrams obtained are useful for visual comprehension of the influence of temperature, sulfur dioxide and moisture on color throughout the time of storage. Close

• 405. [Article] Characterization of high temperature fatigue mechanisms in Haynes 282 nickel based superalloy

  Electric power needs will only grow over the next decades as more humans ascend from poverty into the middle class. Currently, the majority of electric power is generated by burning fossil fuels. To help ...

  Citation × Citation Citation Abstract Copy Title: Characterization of high temperature fatigue mechanisms in Haynes 282 nickel based superalloy Author: Rozman, Kyle A. Electric power needs will only grow over the next decades as more humans ascend from poverty into the middle class. Currently, the majority of electric power is generated by burning fossil fuels. To help mitigate the undesirable effects of burning fossil fuels research is being done to increase the efficiency of power produced. In order to increase the efficiency of power production, the operating temperature of steam turbines must be increased, which presents a materials challenge. Haynes 282 is a nickel based superalloy which has been proposed as a potential rotor alloy for steam turbines operating at high temperature (760°C). Other authors have previously looked at creep, oxidation, low cycle fatigue and other properties of Haynes 282; however, lacking from the literature are studies on the fatigue crack growth mechanisms in Haynes 282. This project investigated Haynes 282 from a fatigue crack growth perspective with an aim to fill this literature gap and assess the utility of Haynes 282 as a steam turbine rotor alloy. This dissertation has specifically evaluated the fatigue crack growth rates of Haynes 282 as functions of temperature and frequency. The testing method utilized was ASTM E647, "Standard test method for measuring fatigue crack growth rates." Temperatures investigated were 550°C, 650°C and 750°C. The loading frequencies were both 25 Hz and 0.25 Hz. In general increasing the test temperature increased fatigue crack growth rate. Thermally activated cross-slip and dislocation annihilation were the primary mechanisms responsible for the increased fatigue crack growth rate. The noted activation energy for dislocation jog migration, which is related to dislocation annihilation, was about 12.5 kJ/mol. This value fit with the measured activation energy. The post-test microstructure showed greatly reduced dislocation density at the highest temperature. Fractography of the crack growth region showed transgranular crack growth at 550°C and 650°C with signs of isolated intergranular features at 750°C. The effect of frequency on the fatigue crack growth rates was minor at 550oC but much more significant at 650°C and 750°C. For the temperatures investigated the effect of decreasing loading frequency was to increase the fatigue crack growth rate. At high loading frequency, the isolated intergranular features were present only at stress intensities below about 11 MPa√m. At 0.25 Hz loading frequency, isolated intergranular features persisted into the high stress intensity range. While the isolated intergranular features are of some concern, the measured activation energy was well below published creep and/or oxidation activation energies. This means the crack path did not have enough energy to sustain an intergranular crack path. In summary, the work discussed in this dissertation investigated the fine details of fatigue crack growth of Haynes 282. This study has closed some of the existing gap in the literature regarding the fatigue crack growth rates of Haynes 282. Previous studies have shown no adverse effects during low cycle fatigue and creep for Haynes 282 at temperatures up to and including 760°C. This study has shown no adverse effects in the fatigue crack growth of Haynes 282 up to 650°C. However, some isolated indications of intergranular crack propagation within the crack growth region were observed at 750°C. These isolated regions were observed to arrest, or to revert back to, transgranular crack propagation. This mechanistic aspect, i.e., change back to transgranular crack propagation, is a promising result. Title: Characterization of high temperature fatigue mechanisms in Haynes 282 nickel based superalloy Author: Rozman, Kyle A. Electric power needs will only grow over the next decades as more humans ascend from poverty into the middle class. Currently, the majority of electric power is generated by burning fossil fuels. To help mitigate the undesirable effects of burning fossil fuels research is being done to increase the efficiency of power produced. In order to increase the efficiency of power production, the operating temperature of steam turbines must be increased, which presents a materials challenge. Haynes 282 is a nickel based superalloy which has been proposed as a potential rotor alloy for steam turbines operating at high temperature (760°C). Other authors have previously looked at creep, oxidation, low cycle fatigue and other properties of Haynes 282; however, lacking from the literature are studies on the fatigue crack growth mechanisms in Haynes 282. This project investigated Haynes 282 from a fatigue crack growth perspective with an aim to fill this literature gap and assess the utility of Haynes 282 as a steam turbine rotor alloy. This dissertation has specifically evaluated the fatigue crack growth rates of Haynes 282 as functions of temperature and frequency. The testing method utilized was ASTM E647, "Standard test method for measuring fatigue crack growth rates." Temperatures investigated were 550°C, 650°C and 750°C. The loading frequencies were both 25 Hz and 0.25 Hz. In general increasing the test temperature increased fatigue crack growth rate. Thermally activated cross-slip and dislocation annihilation were the primary mechanisms responsible for the increased fatigue crack growth rate. The noted activation energy for dislocation jog migration, which is related to dislocation annihilation, was about 12.5 kJ/mol. This value fit with the measured activation energy. The post-test microstructure showed greatly reduced dislocation density at the highest temperature. Fractography of the crack growth region showed transgranular crack growth at 550°C and 650°C with signs of isolated intergranular features at 750°C. The effect of frequency on the fatigue crack growth rates was minor at 550oC but much more significant at 650°C and 750°C. For the temperatures investigated the effect of decreasing loading frequency was to increase the fatigue crack growth rate. At high loading frequency, the isolated intergranular features were present only at stress intensities below about 11 MPa√m. At 0.25 Hz loading frequency, isolated intergranular features persisted into the high stress intensity range. While the isolated intergranular features are of some concern, the measured activation energy was well below published creep and/or oxidation activation energies. This means the crack path did not have enough energy to sustain an intergranular crack path. In summary, the work discussed in this dissertation investigated the fine details of fatigue crack growth of Haynes 282. This study has closed some of the existing gap in the literature regarding the fatigue crack growth rates of Haynes 282. Previous studies have shown no adverse effects during low cycle fatigue and creep for Haynes 282 at temperatures up to and including 760°C. This study has shown no adverse effects in the fatigue crack growth of Haynes 282 up to 650°C. However, some isolated indications of intergranular crack propagation within the crack growth region were observed at 750°C. These isolated regions were observed to arrest, or to revert back to, transgranular crack propagation. This mechanistic aspect, i.e., change back to transgranular crack propagation, is a promising result. Close

• 406. [Article] Soil moisture and temperature relationships under fallow in eastern Oregon

  Time of stand establishment is a critical factor affecting yields of winter wheat and barley in the fallow-crop rotation areas of the Pacific Northwest. Farmers in this winter-rainfall region are dependent ...

  Citation × Citation Citation Abstract Copy Title: Soil moisture and temperature relationships under fallow in eastern Oregon Author: Russelle, Michael P. Time of stand establishment is a critical factor affecting yields of winter wheat and barley in the fallow-crop rotation areas of the Pacific Northwest. Farmers in this winter-rainfall region are dependent on residual moisture in the seed zone for germination, because significant precipitation does not usually occur until after the optimum planting dates. Moisture is maintained near the soil surface through the summer of the fallow period by the use of a soil or stubble mulch. The rate of moisture loss is relatively low during the summer, but seems to accelerate in late August and September. This loss dries the seed zone and forces either deeper planting to reach adequate moisture or delayed seeding until precipitation re-wets the seed zone. Both practices can result in late, less vigorous stands which have lower yield potential and provide less protection from erosion. The objectives of this study were to: 1) quantify changes in seed zone water content prior to seeding; 2) determine the cause of the accelerated loss; 3) substantiate the effect of planting date on the yield of one variety of winter wheat and one variety of winter barley; 4) investigate the effect of soil temperature on the rate of first and 70% emergence of these species in the field; and 5) develop a means of predicting the average last date of planting after which stand establishment is excessively delayed at one location in eastern Oregon. Although both years were abnormally wet in late summer and fall, significant losses of seed zone water content occurred in 1976. At 6 cm, the loss period occurred in early September; at 9, 12, 15, and 18 cm, the losses occurred in late September. The measured losses were not as great as expected. No significant losses were observed in 1977 because of frequent precipitation. My hypothesis was that increasing nighttime vapor pressure gradients from the moist seed zone to the soil surface develop because of the combination of warm days and cool, clear nights characteristic of late August and September in this area. Larger vapor pressure gradients would cause increased water losses from the profile. However, no correlation was found with calculated vapor pressure gradients, the occurrence of low surface temperatures at night, or average temperature gradients in the upper soil profile. Computer simulation of isothermal liquid flow was used to discern the relative contributions of evaporative losses and of long-term redistribution of water In response to gravitational and potential gradients in the profile. Redistribution accounted for 60% of the water loss in the soil beneath the seed zone from mid-July to early August, and accounted for none of the loss from early August to early September. Planting date had a significant effect on yield of both wheat and barley; the optimum planting dates were late September to early October. On each planting date, the seeds were placed in moist soil and covered with approximately 5 cm of soil with a deep furrow drill, so temperature was the primary factor affecting rate of first and 70% emergence. Regression equations of rate of emergence on average 10-cm soil temperature from planting to emergence were highly significant. The degree days needed for first and 70% emergence for wheat were 149 and 210 using a base temperature of 0.7 and 0.4 C, respectively, and for barley were 92 and 159 using base temperatures of 6.1 and 3.5 C, respectively. Soil temperatures from 1963 to 1977 were used to develop a means of predicting average daily 10-cm soil temperature. Using this long-term average and the regression equations of rate of emergence and stand establishment versus temperature, the average last date to plant and still obtain 70% stand in 14 days was 25 September. If seeding is delayed until 15 October, lower soil temperatures will cause the average days to 70% stand of wheat to approach 22-24 days, while barley will require 24 - 2 9 days to reach 70% stand at these temperatures. Title: Soil moisture and temperature relationships under fallow in eastern Oregon Author: Russelle, Michael P. Time of stand establishment is a critical factor affecting yields of winter wheat and barley in the fallow-crop rotation areas of the Pacific Northwest. Farmers in this winter-rainfall region are dependent on residual moisture in the seed zone for germination, because significant precipitation does not usually occur until after the optimum planting dates. Moisture is maintained near the soil surface through the summer of the fallow period by the use of a soil or stubble mulch. The rate of moisture loss is relatively low during the summer, but seems to accelerate in late August and September. This loss dries the seed zone and forces either deeper planting to reach adequate moisture or delayed seeding until precipitation re-wets the seed zone. Both practices can result in late, less vigorous stands which have lower yield potential and provide less protection from erosion. The objectives of this study were to: 1) quantify changes in seed zone water content prior to seeding; 2) determine the cause of the accelerated loss; 3) substantiate the effect of planting date on the yield of one variety of winter wheat and one variety of winter barley; 4) investigate the effect of soil temperature on the rate of first and 70% emergence of these species in the field; and 5) develop a means of predicting the average last date of planting after which stand establishment is excessively delayed at one location in eastern Oregon. Although both years were abnormally wet in late summer and fall, significant losses of seed zone water content occurred in 1976. At 6 cm, the loss period occurred in early September; at 9, 12, 15, and 18 cm, the losses occurred in late September. The measured losses were not as great as expected. No significant losses were observed in 1977 because of frequent precipitation. My hypothesis was that increasing nighttime vapor pressure gradients from the moist seed zone to the soil surface develop because of the combination of warm days and cool, clear nights characteristic of late August and September in this area. Larger vapor pressure gradients would cause increased water losses from the profile. However, no correlation was found with calculated vapor pressure gradients, the occurrence of low surface temperatures at night, or average temperature gradients in the upper soil profile. Computer simulation of isothermal liquid flow was used to discern the relative contributions of evaporative losses and of long-term redistribution of water In response to gravitational and potential gradients in the profile. Redistribution accounted for 60% of the water loss in the soil beneath the seed zone from mid-July to early August, and accounted for none of the loss from early August to early September. Planting date had a significant effect on yield of both wheat and barley; the optimum planting dates were late September to early October. On each planting date, the seeds were placed in moist soil and covered with approximately 5 cm of soil with a deep furrow drill, so temperature was the primary factor affecting rate of first and 70% emergence. Regression equations of rate of emergence on average 10-cm soil temperature from planting to emergence were highly significant. The degree days needed for first and 70% emergence for wheat were 149 and 210 using a base temperature of 0.7 and 0.4 C, respectively, and for barley were 92 and 159 using base temperatures of 6.1 and 3.5 C, respectively. Soil temperatures from 1963 to 1977 were used to develop a means of predicting average daily 10-cm soil temperature. Using this long-term average and the regression equations of rate of emergence and stand establishment versus temperature, the average last date to plant and still obtain 70% stand in 14 days was 25 September. If seeding is delayed until 15 October, lower soil temperatures will cause the average days to 70% stand of wheat to approach 22-24 days, while barley will require 24 - 2 9 days to reach 70% stand at these temperatures. Close

• 407. [Article] Effect of temperature and tissue type on fatty acid signatures of two species of North Pacific juvenile gadids: A laboratory feeding study

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier ...

  Citation × Citation Citation Abstract Copy Title: Effect of temperature and tissue type on fatty acid signatures of two species of North Pacific juvenile gadids: A laboratory feeding study Author: Parrish, Christopher C., Laurel, Benjamin J., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-experimental-marine-biology-and-ecology/. Title: Effect of temperature and tissue type on fatty acid signatures of two species of North Pacific juvenile gadids: A laboratory feeding study Author: Parrish, Christopher C., Laurel, Benjamin J., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-experimental-marine-biology-and-ecology/. Close

• 408. [Article] Individual condition, standard metabolic rate, and rearing temperature influence steelhead and rainbow trout (Oncorhynchus mykiss) life histories

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by NRC Research ...

  Citation × Citation Citation Abstract Copy Title: Individual condition, standard metabolic rate, and rearing temperature influence steelhead and rainbow trout (Oncorhynchus mykiss) life histories Author: Reeves, Gordon H., Sloat, Matthew R. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/journal/cjfas. Title: Individual condition, standard metabolic rate, and rearing temperature influence steelhead and rainbow trout (Oncorhynchus mykiss) life histories Author: Reeves, Gordon H., Sloat, Matthew R. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/journal/cjfas. Close

• 409. [Article] Temperature-dependent growth and behavior of juvenile Arctic cod (Boreogadus saida) and co-occurring North Pacific gadids

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the US Government ...

  Citation × Citation Citation Abstract Copy Title: Temperature-dependent growth and behavior of juvenile Arctic cod (Boreogadus saida) and co-occurring North Pacific gadids Author: Iseri, Paul, Spencer, Mara, Laurel, Benjamin J., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the US Government and published by Springer. It can be found at: http://link.springer.com/journal/300 Title: Temperature-dependent growth and behavior of juvenile Arctic cod (Boreogadus saida) and co-occurring North Pacific gadids Author: Iseri, Paul, Spencer, Mara, Laurel, Benjamin J., Copeman, Louise A. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article is copyrighted by the US Government and published by Springer. It can be found at: http://link.springer.com/journal/300 Close

• 410. [Article] Local atmospheric decoupling in complex topography alters climate change impacts

  Supplementary material included in separate file. This article was originally published in International Journal of Climatology and is copyrighted by the Royal Meteorological Society

  Citation × Citation Citation Abstract Copy Title: Local atmospheric decoupling in complex topography alters climate change impacts Author: Unsworth, Michael H., Daly, Christopher, Conklin, David R. Supplementary material included in separate file. This article was originally published in International Journal of Climatology and is copyrighted by the Royal Meteorological Society Title: Local atmospheric decoupling in complex topography alters climate change impacts Author: Unsworth, Michael H., Daly, Christopher, Conklin, David R. Supplementary material included in separate file. This article was originally published in International Journal of Climatology and is copyrighted by the Royal Meteorological Society Close