Search

Search Results

• 2141. [Article] Interspecific carbon transfer in ectomycorrhizal tree species mixtures

  The overall goal of this study was to investigate influences of ectomycorrhizae (EM) and interspecific carbon transfer on seedling performance in species mixtures. The objectives were to: (I) determine ...

  Citation × Citation Citation Abstract Copy Title: Interspecific carbon transfer in ectomycorrhizal tree species mixtures Author: Simard, S. (Suzanne) The overall goal of this study was to investigate influences of ectomycorrhizae (EM) and interspecific carbon transfer on seedling performance in species mixtures. The objectives were to: (I) determine the potential for EM to link paper birch and Douglas-fir, (ii) quantify gross and net interspecific carbon transfer, and (iii) evaluate effect of transfer on seedling performance. A soil bioassay showed that paper birch and Douglas-fir shared seven EM morphotypes in common over 90% of their root tips, indicating potential for hyphal connections. The number and percent colonization of shared morphotypes were greater when species were grown in dual- than monoculture. Reciprocal labelling of paper birch and Douglas-fir with ¹³CO₂[subscript(gas)] and ¹⁴CO₂[subscript(gas)] in laboratory rootboxes and the field resulted in bi-directional transfer, with net gain by Douglas-fir. In rootboxes, gross and net transfer represented 29% and 4% of total isotope assimilated by both species. Net transfer was three times greater and one-way gross transfer to Douglas-fir 50% greater where interconnecting hyphae were left intact than where severed, but high p-values (p>0.05) leave in question whether hyphal connections facilitated transfer. In the field, gross and net transfer between paper birch and Douglas-fir represented 4% and 2%, respectively, of total isotope assimilated in 1993, and 7% and 6%, respectively, in 1994. Net transfer to Douglas-fir occurred where Douglas-fir grew full sun in 1993, and in all light intensities in 1994. The change in amount transferred and shading effect between years coincided with greater root development and improved seedling vigor in 1994 than 1993. Net and gross transfer were two times greater in 5% than 50% or 100% sun treatments in 1994, suggesting transfer was affected by changes in photosynthate sink strength of Douglas-fir. Isotope transferred to western redcedar represented <1-18% of gross transfer between paper birch and Douglas-fir, indicating most carbon was transferred between EM species via interconnecting hyphae. Douglas-fir seedlings were grown in untrenched and trenched treatments to evaluate the ability of overstory paper birch and Douglas-fir to influence seedling EM inoculation patterns and performance. Greater diversity of EM coincided with higher photosynthesis among seedlings in the untrenched than trenched treatment. The effect on seedling performance was attributed to differences in EM colonization, because trenching had no effect on soil water, soil nutrients, or light availability. Title: Interspecific carbon transfer in ectomycorrhizal tree species mixtures Author: Simard, S. (Suzanne) The overall goal of this study was to investigate influences of ectomycorrhizae (EM) and interspecific carbon transfer on seedling performance in species mixtures. The objectives were to: (I) determine the potential for EM to link paper birch and Douglas-fir, (ii) quantify gross and net interspecific carbon transfer, and (iii) evaluate effect of transfer on seedling performance. A soil bioassay showed that paper birch and Douglas-fir shared seven EM morphotypes in common over 90% of their root tips, indicating potential for hyphal connections. The number and percent colonization of shared morphotypes were greater when species were grown in dual- than monoculture. Reciprocal labelling of paper birch and Douglas-fir with ¹³CO₂[subscript(gas)] and ¹⁴CO₂[subscript(gas)] in laboratory rootboxes and the field resulted in bi-directional transfer, with net gain by Douglas-fir. In rootboxes, gross and net transfer represented 29% and 4% of total isotope assimilated by both species. Net transfer was three times greater and one-way gross transfer to Douglas-fir 50% greater where interconnecting hyphae were left intact than where severed, but high p-values (p>0.05) leave in question whether hyphal connections facilitated transfer. In the field, gross and net transfer between paper birch and Douglas-fir represented 4% and 2%, respectively, of total isotope assimilated in 1993, and 7% and 6%, respectively, in 1994. Net transfer to Douglas-fir occurred where Douglas-fir grew full sun in 1993, and in all light intensities in 1994. The change in amount transferred and shading effect between years coincided with greater root development and improved seedling vigor in 1994 than 1993. Net and gross transfer were two times greater in 5% than 50% or 100% sun treatments in 1994, suggesting transfer was affected by changes in photosynthate sink strength of Douglas-fir. Isotope transferred to western redcedar represented <1-18% of gross transfer between paper birch and Douglas-fir, indicating most carbon was transferred between EM species via interconnecting hyphae. Douglas-fir seedlings were grown in untrenched and trenched treatments to evaluate the ability of overstory paper birch and Douglas-fir to influence seedling EM inoculation patterns and performance. Greater diversity of EM coincided with higher photosynthesis among seedlings in the untrenched than trenched treatment. The effect on seedling performance was attributed to differences in EM colonization, because trenching had no effect on soil water, soil nutrients, or light availability. Close

• 2142. [Article] Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation

  We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes ...

  Citation × Citation Citation Abstract Copy Title: Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation Author: Somes, Christopher J. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO₃ˉ assimilation, water column denitrification, and zooplankton excretion are considered as well as the input of newly fixed nitrogen by diazotrophs. A global database of δ¹⁵NO₃ˉ observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce the observed patterns such as high subsurface values in denitrification zones, the meridional and vertical gradients in the Southern Ocean, and the meridional gradient in the Central Equatorial Pacific. The observed subsurface minimum in the Atlantic is underestimated presumably owing to too little nitrogen fixation there. Sensitivity experiments show that algal NO₃ˉ assimilation, nitrogen fixation and water column denitrification have strong effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotopes distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for diazotrophs and stimulates additional nitrogen fixation. Water column denitrification has a strong but rather localized effect on the nitrogen isotope distribution in model versions without iron limitation of diazotrophy, in which a tight coupling of nitrogen fixation exists. However, including iron limitation of diazotrophy inhibits a tight coupling between water column denitrification and nitrogen fixation in the Eastern Pacific and shifts the main location of nitrogen fixation from the Eastern Tropical Pacific to the Western Tropical Pacific, which results in a better agreement with N' = NO₃ˉ−16PO₄³ˉ and δ¹⁵NO₃ˉ observations. Thus, our model results suggest that iron limitation of diazotrophy can modulate the feedback between denitrification and nitrogen fixation in the ocean. We speculate that a feedback response time on the centennial to millennial time scale may exist between denitrification and nitrogen fixation, producing imbalances in the global oceanic fixed nitrogen cycle, which may well have contributed to past changes of atmospheric CO₂ via the biological pump. Title: Nitrogen isotopes in a global ocean biogeochemical model : constraints on the coupling between denitrification and nitrogen fixation Author: Somes, Christopher J. We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine ecosystem model. The isotope effects of algal NO₃ˉ assimilation, water column denitrification, and zooplankton excretion are considered as well as the input of newly fixed nitrogen by diazotrophs. A global database of δ¹⁵NO₃ˉ observations is compiled from previous studies and compared to the model results on a regional basis where sufficient observations exist. The model is able to qualitatively and quantitatively reproduce the observed patterns such as high subsurface values in denitrification zones, the meridional and vertical gradients in the Southern Ocean, and the meridional gradient in the Central Equatorial Pacific. The observed subsurface minimum in the Atlantic is underestimated presumably owing to too little nitrogen fixation there. Sensitivity experiments show that algal NO₃ˉ assimilation, nitrogen fixation and water column denitrification have strong effects on the simulated distribution of nitrogen isotopes, whereas the effect from zooplankton excretion is weaker. Both water column and sedimentary denitrification also have important indirect effects on the nitrogen isotopes distribution by reducing the fixed nitrogen inventory, which creates an ecological niche for diazotrophs and stimulates additional nitrogen fixation. Water column denitrification has a strong but rather localized effect on the nitrogen isotope distribution in model versions without iron limitation of diazotrophy, in which a tight coupling of nitrogen fixation exists. However, including iron limitation of diazotrophy inhibits a tight coupling between water column denitrification and nitrogen fixation in the Eastern Pacific and shifts the main location of nitrogen fixation from the Eastern Tropical Pacific to the Western Tropical Pacific, which results in a better agreement with N' = NO₃ˉ−16PO₄³ˉ and δ¹⁵NO₃ˉ observations. Thus, our model results suggest that iron limitation of diazotrophy can modulate the feedback between denitrification and nitrogen fixation in the ocean. We speculate that a feedback response time on the centennial to millennial time scale may exist between denitrification and nitrogen fixation, producing imbalances in the global oceanic fixed nitrogen cycle, which may well have contributed to past changes of atmospheric CO₂ via the biological pump. Close

• 2143. [Article] Posting point of sale nutrition information in a college dormitory food court : impact on students' food choice motives and venue sales

  As rates of obesity continue to rise in the United States, interest in restaurant menu labeling has become a growing phenomenon. Many proposed initiatives to require posted nutrition information at the ...

  Citation × Citation Citation Abstract Copy Title: Posting point of sale nutrition information in a college dormitory food court : impact on students' food choice motives and venue sales Author: Frasieur, Amy M. As rates of obesity continue to rise in the United States, interest in restaurant menu labeling has become a growing phenomenon. Many proposed initiatives to require posted nutrition information at the point of sale or decision point for choosing restaurant fare are gaining attention. Research to explore how nutrition labeling may impact food selection, sales and consumer response is limited. The purpose of this study was to explore the various impacts of posting point of sale nutrition information (calories and fat grams) on venue and item sales as well as how food choice motives (FCM), nutrition awareness and purchase choice motives influence choice among subjects in a college dormitory food court. Nutrition information was posted for menu items at two (treatment venues) of seven total venues in a college dormitory food court. Sales data was gathered via ETEK system software to analyze trends in overall sales for all venues and for specific items sales at treatment venues. Survey data was collected before and after the treatment posting, with an N=348 respondents. Results revealed that sales declined in both treatment and some control venues over time. The experimental treatment also revealed that one venue with posted nutrition information showed significant declines in sales transactions during the nutrition information posting period, compared to baseline. Several food items from both of the treatment venues decreased in sales with the posting of nutrition information. Survey data revealed that taste and convenience ranked higher than health in motives driving food choice. Females ranked health and weight control more highly on the scale of food choice motives than males. Food choice motives from surveys were frequently similar to purchase choice motives among respondents, suggesting for this population, FCM may relate to actual purchase. Nutrition awareness was measured by two survey items asking respondents to estimate their own caloric and fat requirements; answering both correctly earned a positive score for nutrition awareness. The females in this study were more likely to earn a positive score for nutrition awareness than males. In general, only half of surveyed respondents noticed the posted nutrition information in the venues and of those who noticed it, fewer than 15% indicated that the posted nutrition information was a strong influence on their purchase choice. Although the posting of nutrition information appeared to have some impact on respondents' food purchases, additional research is needed to understand if college students' value the need to choose healthy fare; the factors that drive food choice among them; and if calorie and fat labeling will impact healthy dining in dormitory food courts. Title: Posting point of sale nutrition information in a college dormitory food court : impact on students' food choice motives and venue sales Author: Frasieur, Amy M. As rates of obesity continue to rise in the United States, interest in restaurant menu labeling has become a growing phenomenon. Many proposed initiatives to require posted nutrition information at the point of sale or decision point for choosing restaurant fare are gaining attention. Research to explore how nutrition labeling may impact food selection, sales and consumer response is limited. The purpose of this study was to explore the various impacts of posting point of sale nutrition information (calories and fat grams) on venue and item sales as well as how food choice motives (FCM), nutrition awareness and purchase choice motives influence choice among subjects in a college dormitory food court. Nutrition information was posted for menu items at two (treatment venues) of seven total venues in a college dormitory food court. Sales data was gathered via ETEK system software to analyze trends in overall sales for all venues and for specific items sales at treatment venues. Survey data was collected before and after the treatment posting, with an N=348 respondents. Results revealed that sales declined in both treatment and some control venues over time. The experimental treatment also revealed that one venue with posted nutrition information showed significant declines in sales transactions during the nutrition information posting period, compared to baseline. Several food items from both of the treatment venues decreased in sales with the posting of nutrition information. Survey data revealed that taste and convenience ranked higher than health in motives driving food choice. Females ranked health and weight control more highly on the scale of food choice motives than males. Food choice motives from surveys were frequently similar to purchase choice motives among respondents, suggesting for this population, FCM may relate to actual purchase. Nutrition awareness was measured by two survey items asking respondents to estimate their own caloric and fat requirements; answering both correctly earned a positive score for nutrition awareness. The females in this study were more likely to earn a positive score for nutrition awareness than males. In general, only half of surveyed respondents noticed the posted nutrition information in the venues and of those who noticed it, fewer than 15% indicated that the posted nutrition information was a strong influence on their purchase choice. Although the posting of nutrition information appeared to have some impact on respondents' food purchases, additional research is needed to understand if college students' value the need to choose healthy fare; the factors that drive food choice among them; and if calorie and fat labeling will impact healthy dining in dormitory food courts. Close

• 2144. [Article] Using Landsat-derived disturbance and recovery history and lidar to map forest biomass dynamics

  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: Using Landsat-derived disturbance and recovery history and lidar to map forest biomass dynamics Author: Yang, Zhiqiang, Cohen, Warren B., Kennedy, Robert E., Pflugmacher, Dirk 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/remote-sensing-of-environment. Title: Using Landsat-derived disturbance and recovery history and lidar to map forest biomass dynamics Author: Yang, Zhiqiang, Cohen, Warren B., Kennedy, Robert E., Pflugmacher, Dirk 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/remote-sensing-of-environment. Close

• 2145. [Article] Risk factors for cardiovascular disease across the spectrum of older age: The Cardiovascular Health 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: Risk factors for cardiovascular disease across the spectrum of older age: The Cardiovascular Health Study Author: Shlipak, Michael G., Whitson, Heather E., et al., Odden, Michelle C. 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/atherosclerosis/. Title: Risk factors for cardiovascular disease across the spectrum of older age: The Cardiovascular Health Study Author: Shlipak, Michael G., Whitson, Heather E., et al., Odden, Michelle C. 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/atherosclerosis/. Close

• 2146. [Article] The effect of El Niño Southern Oscillation cycles on the decadal scale suspended sediment behavior of a coastal dry-summer subtropical catchment

  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 John Wiley ...

  Citation × Citation Citation Abstract Copy Title: The effect of El Niño Southern Oscillation cycles on the decadal scale suspended sediment behavior of a coastal dry-summer subtropical catchment Author: Warrick, Jonathan A., Gray, Andrew B., Pasternack, Gregory B., Watson, Elizabeth B., Goñi, Miguel 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 John Wiley & Sons Ltd. and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291096-9837. Title: The effect of El Niño Southern Oscillation cycles on the decadal scale suspended sediment behavior of a coastal dry-summer subtropical catchment Author: Warrick, Jonathan A., Gray, Andrew B., Pasternack, Gregory B., Watson, Elizabeth B., Goñi, Miguel 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 John Wiley & Sons Ltd. and can be found at: http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291096-9837. Close

• 2147. [Article] Oncogenic KRAS promotes malignant brain tumors in zebrafish

  This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.molecular-cancer.com/.

  Citation × Citation Citation Abstract Copy Title: Oncogenic KRAS promotes malignant brain tumors in zebrafish Author: Chen, Wenbiao, Ju, Bensheng, Taylor, Michael R., Eden, Christopher J., Orr, Brent A., Henson, Hannah E., Spitsbergen, Jan M., Jia, Sujuan This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.molecular-cancer.com/. Title: Oncogenic KRAS promotes malignant brain tumors in zebrafish Author: Chen, Wenbiao, Ju, Bensheng, Taylor, Michael R., Eden, Christopher J., Orr, Brent A., Henson, Hannah E., Spitsbergen, Jan M., Jia, Sujuan This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by BioMed Central Ltd. The published article can be found at: http://www.molecular-cancer.com/. Close

• 2148. [Article] The mobilization of heavy metals from contaminated soil using low molecular weight organic acids

  More than 30,000 potential Superfund sites have been identified. Heavy metals are contaminants at many of these Superfund sites. The average cost of cleanup a single-typical Superfund site currently stands ...

  Citation × Citation Citation Abstract Copy Title: The mobilization of heavy metals from contaminated soil using low molecular weight organic acids Author: Kang, Sun Ki More than 30,000 potential Superfund sites have been identified. Heavy metals are contaminants at many of these Superfund sites. The average cost of cleanup a single-typical Superfund site currently stands at $20 million, and it is expected that the cost may escalate to $50 million within the next decade. Problems have already been encountered during the inspection of sites, and available technologies have not been effective in treating all sites. Lack of innovative strategies for dealing with contaminated soils is a major obstacle to completing Superfund site cleanup. The characteristics of low molecular weight (LMW) organic acids (citric, oxalic, and succinic acids) can be utilized as an agent in soil washing and flushing to develop an innovative technology in the remediation of the soil contaminated with heavy metals. The objective of the work was the testing of a new remediation technology involving soil flushing and washing with LMW organic acids, designed to permanently remove heavy metals from contaminated soil at Superfund sited. Significant amounts of heavy metals (Cu, Pb, Zn) were removed and formed soluble metal-organic complexes at higher concentrations of organic ligands. At a citric concentration of 100 mM, over 70~80% of copper, lead, and zinc were mobilized and all metals extracted were complexed with citrate ions as various forms. Therefore, the use of citric acid to remove heavy metals from contaminated soils would be less costly that using EDTA. The subsequent pH elevation by hydrated lime, Ca(OH)₂, causes the decomplexation of Pb-citrate and initiates precipitation of lead hydroxide. Results showed that slightly alkaline conditions (pH 8.5), which are much lower than that used with EDTA, are needed for substantial precipitative removal of the lead. Increasing calcium nitrate concentration significantly improved the Pb(II) desorption via a cation exchange reaction, That is, the time required to recover lead from the contaminated soil during a soil column experiment was greatly reduced as the concentration of calcium nitrate in the influent was increased. Varying influent pH had little effort on the rate of lead mobilization in the soil columns due to the buffering capacity of the soil, which maintained the effluent pH at the soil pH. The effluent flow rate had no effect on mobilizing Pb(II) from the soil. A higher concentration of citric acid resulted in a much faster rate of lead mobilization from the contaminated soil. Differences in lead desorption rates between influent pHs of 4.5 and 6 were significantly high. However, lead desorption curves for citrate solution at a lower pH value (pH < 4.5) were nearly identical. The flow rate of effluent has no effect at removing lead in the range of 0.1~1.0 mL/min. Also, lead transport model was developed under the assumption of one-dimensional flow through a homogeneous porous medium. A simplified model was also developed by assuming no dispersion effect, no immobile aqueous-phase zone, and linear desorption kinetics. An analytical solution of the simplified equation was obtained by solving a partial differential equation. The computer simulations were fitted to experimental data using estimates for model parameters which were not obtainable independently in experiments. At higher concentrations and pH of the influent, this model presented here fitted well with the experimental data. Title: The mobilization of heavy metals from contaminated soil using low molecular weight organic acids Author: Kang, Sun Ki More than 30,000 potential Superfund sites have been identified. Heavy metals are contaminants at many of these Superfund sites. The average cost of cleanup a single-typical Superfund site currently stands at $20 million, and it is expected that the cost may escalate to $50 million within the next decade. Problems have already been encountered during the inspection of sites, and available technologies have not been effective in treating all sites. Lack of innovative strategies for dealing with contaminated soils is a major obstacle to completing Superfund site cleanup. The characteristics of low molecular weight (LMW) organic acids (citric, oxalic, and succinic acids) can be utilized as an agent in soil washing and flushing to develop an innovative technology in the remediation of the soil contaminated with heavy metals. The objective of the work was the testing of a new remediation technology involving soil flushing and washing with LMW organic acids, designed to permanently remove heavy metals from contaminated soil at Superfund sited. Significant amounts of heavy metals (Cu, Pb, Zn) were removed and formed soluble metal-organic complexes at higher concentrations of organic ligands. At a citric concentration of 100 mM, over 70~80% of copper, lead, and zinc were mobilized and all metals extracted were complexed with citrate ions as various forms. Therefore, the use of citric acid to remove heavy metals from contaminated soils would be less costly that using EDTA. The subsequent pH elevation by hydrated lime, Ca(OH)₂, causes the decomplexation of Pb-citrate and initiates precipitation of lead hydroxide. Results showed that slightly alkaline conditions (pH 8.5), which are much lower than that used with EDTA, are needed for substantial precipitative removal of the lead. Increasing calcium nitrate concentration significantly improved the Pb(II) desorption via a cation exchange reaction, That is, the time required to recover lead from the contaminated soil during a soil column experiment was greatly reduced as the concentration of calcium nitrate in the influent was increased. Varying influent pH had little effort on the rate of lead mobilization in the soil columns due to the buffering capacity of the soil, which maintained the effluent pH at the soil pH. The effluent flow rate had no effect on mobilizing Pb(II) from the soil. A higher concentration of citric acid resulted in a much faster rate of lead mobilization from the contaminated soil. Differences in lead desorption rates between influent pHs of 4.5 and 6 were significantly high. However, lead desorption curves for citrate solution at a lower pH value (pH < 4.5) were nearly identical. The flow rate of effluent has no effect at removing lead in the range of 0.1~1.0 mL/min. Also, lead transport model was developed under the assumption of one-dimensional flow through a homogeneous porous medium. A simplified model was also developed by assuming no dispersion effect, no immobile aqueous-phase zone, and linear desorption kinetics. An analytical solution of the simplified equation was obtained by solving a partial differential equation. The computer simulations were fitted to experimental data using estimates for model parameters which were not obtainable independently in experiments. At higher concentrations and pH of the influent, this model presented here fitted well with the experimental data. Close

• 2149. [Article] A morphological, physiological and gentic investigation of the African pygmy goat

  Six groups of goats were used in the study. These were the normal group (Saanen, French Alpine, and Nubian breeds), 1/4 pygmy group (first backcross to normal), 1/2 pygmy group (F1) 3/4 pygmy group (first ...

  Citation × Citation Citation Abstract Copy Title: A morphological, physiological and gentic investigation of the African pygmy goat Author: Blanks, George Anthony Six groups of goats were used in the study. These were the normal group (Saanen, French Alpine, and Nubian breeds), 1/4 pygmy group (first backcross to normal), 1/2 pygmy group (F1) 3/4 pygmy group (first backcross to pygmy), 7/8 pygmy group (second backcross to pygmy), and pygmy group0 The mean weight of the 1/2 pygmy group approximated more closely that of the normal group than that of the pygmy group. The mean weight of the 1/4 pygmy group approximated that of the normal group more closely than the mean weight of the 1/2 pygmy group. The mean weight of the 3/4 pygmy group approximated the mean weight of the 1/2 pygmy group more closely than that of the pygmy group. The same relationships among groups that were observed for the weights were also observed for the 12 and 24 week measurements, and the 15 month weights and measurements. As the relationship to the pure pygmy group increased, the goats became proportionally deeper, wider, longer and greater in circumference than would have been expected on the basis of the measurements of the normal goats In the same manner, as the relationship to the pygmy increased, the weights and measurements of the internal organs increased above that expected on the basis of weights and measurements of the normal goats Three blood chemicals, amino acid nitrogen, urea nitrogen, and alkaline phosphatase, were examined at 4, 6, 8, 10, 12, 16, 20, and 24 weeks of age. Amino acid nitrogen did not change significantly with increasing age or weight. However, the level generally decreased in the six groups during the preweaning period, and increased during the postweaning period. Urea nitrogen levels in creased significantly in both sexes as age and weight increased The levels of urea nitrogen increased during both the preweaning and postweaning periods. Alkaline phosphatase activity decreased significantly with increasing age, but showed no significant association with changes in weight. Three levels of alkaline phosphatase activity were observed; high, medium, and low. All three levels were found in the normal, 1/4 pygmy, and 1/2 pygmy groups The medium and low level were found in the 3/4 pygmy, and 7/8 pygmy groups. Only the low level was found in the pygmy group0 The low point in alkaline phosphatase activity was found during the period following weaning. A genetic model was proposed for the inheritance of the pygmy characteristic. The proposed model consists of two genes, a major gene and a modifier gene. The effect of the major gene is to produce large changes in the size of the animals, while the effect of the modifier gene is to regulate the effectiveness of the major gene. Both appear to show incomplete dominance when in the heterozygous condition. The genotype of the normal goats was proposed as being NNaa, that of the pygmy as being nnAA, and that of the 1/2 pygmy as being NnAa where N and n are alleles of the major gene, and A and a are alleles of the modifier gene, Using the weight of the normal goat as a standard, the theoretical values of each possible genotype in each group was calculated. Theoretical means were calculated for each of the groups and found not to be significantly different from the means actually obtained. Title: A morphological, physiological and gentic investigation of the African pygmy goat Author: Blanks, George Anthony Six groups of goats were used in the study. These were the normal group (Saanen, French Alpine, and Nubian breeds), 1/4 pygmy group (first backcross to normal), 1/2 pygmy group (F1) 3/4 pygmy group (first backcross to pygmy), 7/8 pygmy group (second backcross to pygmy), and pygmy group0 The mean weight of the 1/2 pygmy group approximated more closely that of the normal group than that of the pygmy group. The mean weight of the 1/4 pygmy group approximated that of the normal group more closely than the mean weight of the 1/2 pygmy group. The mean weight of the 3/4 pygmy group approximated the mean weight of the 1/2 pygmy group more closely than that of the pygmy group. The same relationships among groups that were observed for the weights were also observed for the 12 and 24 week measurements, and the 15 month weights and measurements. As the relationship to the pure pygmy group increased, the goats became proportionally deeper, wider, longer and greater in circumference than would have been expected on the basis of the measurements of the normal goats In the same manner, as the relationship to the pygmy increased, the weights and measurements of the internal organs increased above that expected on the basis of weights and measurements of the normal goats Three blood chemicals, amino acid nitrogen, urea nitrogen, and alkaline phosphatase, were examined at 4, 6, 8, 10, 12, 16, 20, and 24 weeks of age. Amino acid nitrogen did not change significantly with increasing age or weight. However, the level generally decreased in the six groups during the preweaning period, and increased during the postweaning period. Urea nitrogen levels in creased significantly in both sexes as age and weight increased The levels of urea nitrogen increased during both the preweaning and postweaning periods. Alkaline phosphatase activity decreased significantly with increasing age, but showed no significant association with changes in weight. Three levels of alkaline phosphatase activity were observed; high, medium, and low. All three levels were found in the normal, 1/4 pygmy, and 1/2 pygmy groups The medium and low level were found in the 3/4 pygmy, and 7/8 pygmy groups. Only the low level was found in the pygmy group0 The low point in alkaline phosphatase activity was found during the period following weaning. A genetic model was proposed for the inheritance of the pygmy characteristic. The proposed model consists of two genes, a major gene and a modifier gene. The effect of the major gene is to produce large changes in the size of the animals, while the effect of the modifier gene is to regulate the effectiveness of the major gene. Both appear to show incomplete dominance when in the heterozygous condition. The genotype of the normal goats was proposed as being NNaa, that of the pygmy as being nnAA, and that of the 1/2 pygmy as being NnAa where N and n are alleles of the major gene, and A and a are alleles of the modifier gene, Using the weight of the normal goat as a standard, the theoretical values of each possible genotype in each group was calculated. Theoretical means were calculated for each of the groups and found not to be significantly different from the means actually obtained. Close

• 2150. [Article] Stream protection and three timber falling techniques : a comparison of costs and benefits

  The objective of this study was to quantify the amounts of logging residues that are added to mountain stream channels as a result of timber falling - logging procedures, and to evaluate these procedures ...

  Citation × Citation Citation Abstract Copy Title: Stream protection and three timber falling techniques : a comparison of costs and benefits Author: McGreer, Dale Jay The objective of this study was to quantify the amounts of logging residues that are added to mountain stream channels as a result of timber falling - logging procedures, and to evaluate these procedures with respect to both ecologic and economic considerations. Three falling - logging treatments were observed: Conventional falling, Cable-assist falling, and Conventional falling with streamside buffer strips. Streamside environmental impact was evaluated in terms of the potential for damage due to the addition of organic logging residues to stream channels. Economic considerations included stream debris removal, timber volume left unharvested in buffer strips, timber falling labor and equipment, and timber breakage. H Stream debris was quantifie& for ten headwater streams in western Oregon prior to logging, after falling, and after yarding. To determine timber falling breakage and direct falling costs for both conventional and cable-assist methods, over 1.6 million board feet of timber was observed during falling operations. Results show that buffer strips were most effective in preventing logging debris from reaching stream channels. A 160 foot wide buffer strip allowed no debris penetration. During falling operations, 1.8 and 2.0 tons of debris per 100 feet of stream penetrated buffers with widths of 36 and 15 feet respecttively. Conventional falling added an average of 47 tons of debris per 100 feet of stream. Cable-assist falling added only 14 tons per station, thus demonstrating its applicability as a stream protection technique. Stream debris removal costs were found to be quite low for the observed buffer strip units. Estimated clean-up costs for the conventional falling treatment averaged $400 per station compared to only $154 per station for cable-assist falling. Timber falling production rates averaged 9.3 MBF per hour for conventional falling, and 6.3 MBF per hour for cable-assist falling. Due to lower production rates, larger falling crews, and additional machinery costs, direct falling costs for cableassist falling averaged $8.02 per NBF (gross scale) compared to $3.33 per MBF for conventional failing. Timber breakage averaged 7.35 percent of gross scale for conventional falling compared to 5.92 percent for cable-assist falling, a difference. of 1.43 percent. For both methods, breakage increased as trees became larger and more defective. The total cost of the economic factors evaluated was applied to a hypothetical 40 acre setting of 2,800 MBF. The analysis showed that of all treatments, the narrow 15 foot wide buffer strip treatment was most economical, total cost being only $6.12 per MBF. Due to the high cost of leaving 285 NBF of timber the 160 foot wide buffer strip treatment was most expensive at $13.18 per MBF. For the conventional falling - logging treatment, the total cost per MEF was $7.93. This compares with $10.96 per MBF for cable-assist falling; savings of breakage and stream debris removal costs were offset by much higher direct falling costs. Although not included as a cost consideration in this analysis, cable-assist falling produced a greater average log length than did conventional falling. Consideration of log length relationships, and use of higher stumpage values would have altered the outcome of this analysis. The cable-assist treatment would have become more economically desirable compared to the conventional and buffer strip treatments. Title: Stream protection and three timber falling techniques : a comparison of costs and benefits Author: McGreer, Dale Jay The objective of this study was to quantify the amounts of logging residues that are added to mountain stream channels as a result of timber falling - logging procedures, and to evaluate these procedures with respect to both ecologic and economic considerations. Three falling - logging treatments were observed: Conventional falling, Cable-assist falling, and Conventional falling with streamside buffer strips. Streamside environmental impact was evaluated in terms of the potential for damage due to the addition of organic logging residues to stream channels. Economic considerations included stream debris removal, timber volume left unharvested in buffer strips, timber falling labor and equipment, and timber breakage. H Stream debris was quantifie& for ten headwater streams in western Oregon prior to logging, after falling, and after yarding. To determine timber falling breakage and direct falling costs for both conventional and cable-assist methods, over 1.6 million board feet of timber was observed during falling operations. Results show that buffer strips were most effective in preventing logging debris from reaching stream channels. A 160 foot wide buffer strip allowed no debris penetration. During falling operations, 1.8 and 2.0 tons of debris per 100 feet of stream penetrated buffers with widths of 36 and 15 feet respecttively. Conventional falling added an average of 47 tons of debris per 100 feet of stream. Cable-assist falling added only 14 tons per station, thus demonstrating its applicability as a stream protection technique. Stream debris removal costs were found to be quite low for the observed buffer strip units. Estimated clean-up costs for the conventional falling treatment averaged $400 per station compared to only $154 per station for cable-assist falling. Timber falling production rates averaged 9.3 MBF per hour for conventional falling, and 6.3 MBF per hour for cable-assist falling. Due to lower production rates, larger falling crews, and additional machinery costs, direct falling costs for cableassist falling averaged $8.02 per NBF (gross scale) compared to $3.33 per MBF for conventional failing. Timber breakage averaged 7.35 percent of gross scale for conventional falling compared to 5.92 percent for cable-assist falling, a difference. of 1.43 percent. For both methods, breakage increased as trees became larger and more defective. The total cost of the economic factors evaluated was applied to a hypothetical 40 acre setting of 2,800 MBF. The analysis showed that of all treatments, the narrow 15 foot wide buffer strip treatment was most economical, total cost being only $6.12 per MBF. Due to the high cost of leaving 285 NBF of timber the 160 foot wide buffer strip treatment was most expensive at $13.18 per MBF. For the conventional falling - logging treatment, the total cost per MEF was $7.93. This compares with $10.96 per MBF for cable-assist falling; savings of breakage and stream debris removal costs were offset by much higher direct falling costs. Although not included as a cost consideration in this analysis, cable-assist falling produced a greater average log length than did conventional falling. Consideration of log length relationships, and use of higher stumpage values would have altered the outcome of this analysis. The cable-assist treatment would have become more economically desirable compared to the conventional and buffer strip treatments. Close