Background: Increasingly, drug and device clinical trials are tracking activity levels and other ... more Background: Increasingly, drug and device clinical trials are tracking activity levels and other quality of life indices as endpoints for therapeutic efficacy. Trials have traditionally required intermittent subject visits to the clinic that are artificial, activity-intensive, and infrequent, making trend and event detection between visits difficult. Thus, there is an unmet need for wearable sensors that produce clinical quality and medical grade physiological data from subjects in the home. The current study was designed to validate the BioStamp nPoint ® system (MC10 Inc., Lexington, MA, USA), a new technology designed to meet this need. Objective: To evaluate the accuracy, performance, and ease of use of an end-to-end system called the BioStamp nPoint. The system consists of an investigator portal for design of trials and data review, conformal, low-profile, wearable biosensors that adhere to the skin, a companion technology for wireless data transfer to a proprietary cloud, and algorithms for analyzing physiological, biometric, and contextual data for clinical research. Methods: A prospective, nonrandomized clinical trial was conducted on 30 healthy adult volunteers over the course of two continuous days and nights. Supervised and unsupervised study activities enabled performance validation in clinical and remote (simulated "at home") environments. System outputs for heart rate (HR), heart rate variability (HRV) (including root mean square of successive differences [RMSSD] and low frequency/high frequency ratio), activity classifi
Using individual (not summated) Likert-type items (questions) as measurement tools is common in a... more Using individual (not summated) Likert-type items (questions) as measurement tools is common in agricultural education research. The Journal of Agricultural Education published 188 research articles in Volumes 27 through 32. Responses to individual Likert-type items on measurement instruments were analyzed in 95, or more than half, of these articles. After reviewing the articles analyzing individual Likert-type items, 5 1 (54%) reported only descriptive statistics (e.g., means, standard deviations, frequencies/percentages by category). Paired Likert-type items or sets of items were compared using nonparametric statistical techniques (e.g., chi-square homogeneity tests, Mann-Whitney-Wilcoxon U tests, Kruskal-Wallis analysis of variance tests) in 12 (13%) of the articles. Means for paired Likert-type items were compared using parametric statistical procedures (e.g. t-tests or analysis of variance F-tests) in 32 (34%) of the articles.
In agricultural education, both 4-H and FFA have identified leadership development as central to ... more In agricultural education, both 4-H and FFA have identified leadership development as central to their mission. Many Cooperative Extension Service and agricultural educators, members, and alumni think these organizations provide effective leadership programming. However, there is little research to support that viewpoint. The purpose of this study was to develop a valid, reliable scale to measure youth leadership life skills development. The first phase involved the conceptualization and operationalization of youth leadership life skills development (YLLSD). YLLSD was conceptualized as having seven sub-domains (Miller, 1976) and operationalized with 68 indicators. Each indicator used a four point Likert-type subscale. Face and content validity were assessed by a panel of experts. In the second phase, construct validity, reliability, and dimensionality were assessed. Data were collected during September and October, 1992, following the Dillman procedure. The target population was 6,388 senior 4-H and FFA members from New Mexico. A random sample of 400, stratified proportionally to ensure organizational representation was generated. A usable return rate of 66% was obtained. No differences were found between respondents and nonrespondents. During construct validity assessment, indicators of youth leadership life skills development were eliminated through item analysis, internal structure relationships, and cross-structure relationships. The final summated scale of 30 indicators had a Cronbach's alpha reliability coefficient of .98. Factor analysis was used to assess dimensionality. Although the final scale contains indicators from the seven original conceptual domains, youth in the study perceived the construct to be unidimensional.
In many data analytical applications involving the comparison of means from several populations, ... more In many data analytical applications involving the comparison of means from several populations, analyses are adjusted by including one or more continuous variables in the model. Such an analysis is often called an Analysis of Covariance. In this study, we examine the effect of such an adjustment on the precision of inferences regarding the adjusted means and the interpretation of those means. We consider the variance of the difference between a pair of adjusted means and show that the variance is minimized when the mean of the covariate is the same in both groups. However, when the covariate means differ across groups, the additional term in the model can dominate the variance of the comparison. We investigate the break-even point for this comparison and under what condition that occurs. Finally, we demonstrate, with several data sets, how these results may be manifested in practice. here are a variety of analytical procedures that have been developed for use in comparing the performance of individuals in two or more groups. With only one variable and two groups, a simple t-test will suffice in most instances. With additional groups involved in the comparison, a straightforward extension of the independent samples t-test to a one-way analysis of variance (ANOVA) is common (see Dowdy, Weardon, & Chilko, 2004; Glass & Hopkins, 1996). More advanced procedures allow for the inclusion of additional variables in the analysis, which are sometimes called independent or predictor variables. When a second categorical variable is included, the analysis may be referred to as a two-factor ANOVA, or a randomized complete block design, depending on the context of the analysis and the research design employed. When the additional predictor variable is numerical, the analysis is typically called an analysis of covariance (ANCOVA) and the numerical predictor is commonly called a covariate. These last two scenarios are easily extended conceptually to allow for the inclusion of additional predictors/covariates, if desired. The focus of this research is on ANCOVA and, in particular, the interpretation of the adjusted means from such analyses. Most modern textbooks addressing experimental design include chapters or sections on the methods of ANCOVA (see Hicks & Turner, 1999; Kuehl, 2000; Montgomery, 2009). Fisher (1934) stated that ANCOVA "combines the advantages and reconciles the requirements of. .. regression and analysis of variance" (p. 281). Cochran (1957) summarized the theory, nature, and use of ANCOVA and identified some potential problems and misuses of the procedure. One of the most frequent uses Cochran identified was "to increase precision in randomized experiments" (p. 262). Typically, this increased precision was accomplished by making preliminary measurements on experimental units prior to applying treatments. He noted, however, that it was not uncommon for the covariate to be measured on a different scale than that of the response variable and used reading performance adjusted for initial IQ scores as an example. In situations such as these, it is important to verify that treatments have had no effect on the covariate. Cochran further explained that
s d a. go v You can find additional information about ERS publications, databases, and other prod... more s d a. go v You can find additional information about ERS publications, databases, and other products at our website.
Japan is a leading market for U.S. oranges. Since 1995, orange consumption in Japan has declined.... more Japan is a leading market for U.S. oranges. Since 1995, orange consumption in Japan has declined. This report summarizes an analysis of household survey data to assess various factors that may be related to the decline. Consumption of oranges in Japan differs markedly across generations, with younger generations (cohorts) eating fewer oranges than older generations. However, within generations, as individuals in Japan grow older, they eat more oranges. On balance, the effects on consumption associated with aging and birth cohort membership are mostly offsetting. Orange prices affect consumption levels, but household income does not. Even after the analysis accounts for price and demographic variables, a strong downward trend is evident in orange consumption in Japan. Results suggest that orange consumption could decline even more in the future.
In many data analytical applications involving the comparison of means from several populations, ... more In many data analytical applications involving the comparison of means from several populations, analyses are adjusted by including one or more continuous variables in the model. Such an analysis is often called an Analysis of Covariance. In this study, we examine the effect of such an adjustment on the precision of inferences regarding the adjusted means and the interpretation of those means. We consider the variance of the difference between a pair of adjusted means and show that the variance is minimized when the mean of the covariate is the same in both groups. However, when the covariate means differ across groups, the additional term in the model can dominate the variance of the comparison. We investigate the break-even point for this comparison and under what condition that occurs. Finally, we demonstrate, with several data sets, how these results may be manifested in practice. here are a variety of analytical procedures that have been developed for use in comparing the perfo...
In agricultural education, both 4-H and FFA have identified leadership development as central to ... more In agricultural education, both 4-H and FFA have identified leadership development as central to their mission. Many Cooperative Extension Service and agricultural educators, members, and alumni think these organizations provide effective leadership programming. However, there is little research to support that viewpoint. The purpose of this study was to develop a valid, reliable scale to measure youth leadership life skills development. The first phase involved the conceptualization and operationalization of youth leadership life skills development (YLLSD). YLLSD was conceptualized as having seven sub-domains (Miller, 1976) and operationalized with 68 indicators. Each indicator used a four point Likert-type subscale. Face and content validity were assessed by a panel of experts. In the second phase, construct validity, reliability, and dimensionality were assessed. Data were collected during September and October, 1992, following the Dillman procedure. The target population was 6,3...
Conference on Applied Statistics in Agriculture, 1992
We investigate three alternative models for estimating the mean of a population using double samp... more We investigate three alternative models for estimating the mean of a population using double sampling survey techniques. One estimator was found in the range science literature (Cook and stubbendieck, 1986), another is the estimator presented by Cochran (1977). The third estimator uses method-ofmoments estimators with measurement error regression models. Simulation studies suggest that the measurement error model does not work well when the slope is appreciably different from unity. Delta method variance estimators of the measurement error model may give negative variance estimates under these circumstances. The other estimators have better small sample performance (both are approximately unbiased, and have similar variances), but the two estimators have very different estimated variances under some circumstances.
Due to a rapidly aging society, stagnating per capita income and rather stable prices, traditiona... more Due to a rapidly aging society, stagnating per capita income and rather stable prices, traditional economic analyses methods lost their power in the 1990s to predict future food product consumption in Japan. This study, in part, remedies this problem by projecting future consumption of selected products, using a cohort approach with economic factors tentatively set aside. Per capita consumption of individual household members by age was derived by incorporating family age composition into household data classified by age groups of household head (HH). Individual consumption estimates were decomposed into age, cohort and time effects, using the Nakamura's Bayesian cohort model. These effects were synthesized to predict per capita consumption in each population age cell in 2010 and 2020. Although some method refinement is warranted, the cohort approach proves a useful tool in improving prediction of future food product consumption and, combined with economic factors, may prove use...
Tests of theories that attempt to explain why individuals currently use drugs are widespread; how... more Tests of theories that attempt to explain why individuals currently use drugs are widespread; however, the theoretical examinations of abstention from drugs and the cessation of their use are rare. For its part, social learning theory has been supported consistently in its delineation of the process by which substance use is learned. We propose that cessation and abstention are also learned behavior, Using logistic regression analysis, we examine the ability of social learning variables to distinguish among abstainers, current users, and former users of illicit drugs within a sample of 1688 middle-and high-school students in two widely separated nonurban communities. Results indicate that social learning variables clearly distinguish abstainers from current users but are less able to distinguish former users and current users or former users from abstainers. The theoretical, research, and policy implications of these findings are examined in detail.
Broom snakeweed achene dispersal was monitored by placing surface-level traps outwards in the car... more Broom snakeweed achene dispersal was monitored by placing surface-level traps outwards in the cardinal directions from 12 plants and collecting the achenes weekly or biweekly from September 1993 until seeds were no longer retained by the plants after 42 wk. About 50% of the achenes dispersed between October and December. Especially high numbers of achenes were dislodged during periods of intense winter winds and rains, with 78% of the seed placed into the east tray and 86% falling within 50 cm of the parent plant. Achene production averaged 3,928 (± 1,146) per plant in 1993 and 2,036 (± 987) per plant in 1994. Achenes collected over time directly from the inflorescence and achenes stored in nylon packets on the soil surface averaged 82% viability during fall and winter. Achene viability declined rapidly in late spring, and few remained viable before the next seed crop. Greenhouse experiments compared the influence of water application interval and water amount on broom snakeweed ger...
Experiments were conducted to determine variation of in vitro microsclerotia production, pigmenta... more Experiments were conducted to determine variation of in vitro microsclerotia production, pigmentation, and growth of five Pyrenochaeta terrestris (Hans.) Gorenz, Walker, and Larson isolates from Texas and New Mexico. Isolates of P. terrestris, the causal agent of pink root rot, were placed on agar with lo-mm-long sections of sterile onion (Allium cepa L.) roots. Microsclerotia were present after 20 days at 20, 25, 27, or 32C, with the number of microsclerotia dependent on the isolate. Microsclerotia were absent at 35C. One isolate produced few microsclerotia at all temperatures. Optimum temperatures for growth on potato dextrose agar for the isolates tested were 25 and 27C. Pigment production in roots on agar varied depending on isolate and temperature. Three isolates produced high levels of pigment in onion roots at 15, 20, 25, and 27C. A New Mexico isolate produced significantly less visible pigment than the other New Mexico and Texas isolates. One isolate produced very little pig...
Conference on Applied Statistics in Agriculture, 1990
An FI interspecific hybrid onion (Allium cepa x A..:.. fistulosum) was backcrossed to the A..:.. ... more An FI interspecific hybrid onion (Allium cepa x A..:.. fistulosum) was backcrossed to the A..:.. cepa parent line under field conditions. The progeny of this cross were shown by electrophoretic protein analysis to be a mixture of BC l (the desired backcross) and F2 (A..:.. cepa x A..:.. fistulosum) x (A..:.. cepa x A..:.. fistulosum)individuals. This mixture of populations among the progeny render the usual X 2 test for independent segregation of loci invalid. F2 is used to denote progeny derived from either selfing of the Fl or from sib-crosses between two Fl individuals. A model for this mixed population has been developed; from this model the mixture fraction and crossover frequencies can be estimated using maximum likelihood.
... Bionomics of Cleonidius trivittatus (Coleoptera: Curculionidae): Native Biological Control of... more ... Bionomics of Cleonidius trivittatus (Coleoptera: Curculionidae): Native Biological Control of Purple Locoweed (Rosales: Fabaceae) ... Twenty-five1.0-m2 quadrats were sampled every 2 wk from 28 March to 26 September 1992 and every 3 wk from 15 April to 4 September 1993 to ...
Background: Increasingly, drug and device clinical trials are tracking activity levels and other ... more Background: Increasingly, drug and device clinical trials are tracking activity levels and other quality of life indices as endpoints for therapeutic efficacy. Trials have traditionally required intermittent subject visits to the clinic that are artificial, activity-intensive, and infrequent, making trend and event detection between visits difficult. Thus, there is an unmet need for wearable sensors that produce clinical quality and medical grade physiological data from subjects in the home. The current study was designed to validate the BioStamp nPoint ® system (MC10 Inc., Lexington, MA, USA), a new technology designed to meet this need. Objective: To evaluate the accuracy, performance, and ease of use of an end-to-end system called the BioStamp nPoint. The system consists of an investigator portal for design of trials and data review, conformal, low-profile, wearable biosensors that adhere to the skin, a companion technology for wireless data transfer to a proprietary cloud, and algorithms for analyzing physiological, biometric, and contextual data for clinical research. Methods: A prospective, nonrandomized clinical trial was conducted on 30 healthy adult volunteers over the course of two continuous days and nights. Supervised and unsupervised study activities enabled performance validation in clinical and remote (simulated "at home") environments. System outputs for heart rate (HR), heart rate variability (HRV) (including root mean square of successive differences [RMSSD] and low frequency/high frequency ratio), activity classifi
Using individual (not summated) Likert-type items (questions) as measurement tools is common in a... more Using individual (not summated) Likert-type items (questions) as measurement tools is common in agricultural education research. The Journal of Agricultural Education published 188 research articles in Volumes 27 through 32. Responses to individual Likert-type items on measurement instruments were analyzed in 95, or more than half, of these articles. After reviewing the articles analyzing individual Likert-type items, 5 1 (54%) reported only descriptive statistics (e.g., means, standard deviations, frequencies/percentages by category). Paired Likert-type items or sets of items were compared using nonparametric statistical techniques (e.g., chi-square homogeneity tests, Mann-Whitney-Wilcoxon U tests, Kruskal-Wallis analysis of variance tests) in 12 (13%) of the articles. Means for paired Likert-type items were compared using parametric statistical procedures (e.g. t-tests or analysis of variance F-tests) in 32 (34%) of the articles.
In agricultural education, both 4-H and FFA have identified leadership development as central to ... more In agricultural education, both 4-H and FFA have identified leadership development as central to their mission. Many Cooperative Extension Service and agricultural educators, members, and alumni think these organizations provide effective leadership programming. However, there is little research to support that viewpoint. The purpose of this study was to develop a valid, reliable scale to measure youth leadership life skills development. The first phase involved the conceptualization and operationalization of youth leadership life skills development (YLLSD). YLLSD was conceptualized as having seven sub-domains (Miller, 1976) and operationalized with 68 indicators. Each indicator used a four point Likert-type subscale. Face and content validity were assessed by a panel of experts. In the second phase, construct validity, reliability, and dimensionality were assessed. Data were collected during September and October, 1992, following the Dillman procedure. The target population was 6,388 senior 4-H and FFA members from New Mexico. A random sample of 400, stratified proportionally to ensure organizational representation was generated. A usable return rate of 66% was obtained. No differences were found between respondents and nonrespondents. During construct validity assessment, indicators of youth leadership life skills development were eliminated through item analysis, internal structure relationships, and cross-structure relationships. The final summated scale of 30 indicators had a Cronbach's alpha reliability coefficient of .98. Factor analysis was used to assess dimensionality. Although the final scale contains indicators from the seven original conceptual domains, youth in the study perceived the construct to be unidimensional.
In many data analytical applications involving the comparison of means from several populations, ... more In many data analytical applications involving the comparison of means from several populations, analyses are adjusted by including one or more continuous variables in the model. Such an analysis is often called an Analysis of Covariance. In this study, we examine the effect of such an adjustment on the precision of inferences regarding the adjusted means and the interpretation of those means. We consider the variance of the difference between a pair of adjusted means and show that the variance is minimized when the mean of the covariate is the same in both groups. However, when the covariate means differ across groups, the additional term in the model can dominate the variance of the comparison. We investigate the break-even point for this comparison and under what condition that occurs. Finally, we demonstrate, with several data sets, how these results may be manifested in practice. here are a variety of analytical procedures that have been developed for use in comparing the performance of individuals in two or more groups. With only one variable and two groups, a simple t-test will suffice in most instances. With additional groups involved in the comparison, a straightforward extension of the independent samples t-test to a one-way analysis of variance (ANOVA) is common (see Dowdy, Weardon, & Chilko, 2004; Glass & Hopkins, 1996). More advanced procedures allow for the inclusion of additional variables in the analysis, which are sometimes called independent or predictor variables. When a second categorical variable is included, the analysis may be referred to as a two-factor ANOVA, or a randomized complete block design, depending on the context of the analysis and the research design employed. When the additional predictor variable is numerical, the analysis is typically called an analysis of covariance (ANCOVA) and the numerical predictor is commonly called a covariate. These last two scenarios are easily extended conceptually to allow for the inclusion of additional predictors/covariates, if desired. The focus of this research is on ANCOVA and, in particular, the interpretation of the adjusted means from such analyses. Most modern textbooks addressing experimental design include chapters or sections on the methods of ANCOVA (see Hicks & Turner, 1999; Kuehl, 2000; Montgomery, 2009). Fisher (1934) stated that ANCOVA "combines the advantages and reconciles the requirements of. .. regression and analysis of variance" (p. 281). Cochran (1957) summarized the theory, nature, and use of ANCOVA and identified some potential problems and misuses of the procedure. One of the most frequent uses Cochran identified was "to increase precision in randomized experiments" (p. 262). Typically, this increased precision was accomplished by making preliminary measurements on experimental units prior to applying treatments. He noted, however, that it was not uncommon for the covariate to be measured on a different scale than that of the response variable and used reading performance adjusted for initial IQ scores as an example. In situations such as these, it is important to verify that treatments have had no effect on the covariate. Cochran further explained that
s d a. go v You can find additional information about ERS publications, databases, and other prod... more s d a. go v You can find additional information about ERS publications, databases, and other products at our website.
Japan is a leading market for U.S. oranges. Since 1995, orange consumption in Japan has declined.... more Japan is a leading market for U.S. oranges. Since 1995, orange consumption in Japan has declined. This report summarizes an analysis of household survey data to assess various factors that may be related to the decline. Consumption of oranges in Japan differs markedly across generations, with younger generations (cohorts) eating fewer oranges than older generations. However, within generations, as individuals in Japan grow older, they eat more oranges. On balance, the effects on consumption associated with aging and birth cohort membership are mostly offsetting. Orange prices affect consumption levels, but household income does not. Even after the analysis accounts for price and demographic variables, a strong downward trend is evident in orange consumption in Japan. Results suggest that orange consumption could decline even more in the future.
In many data analytical applications involving the comparison of means from several populations, ... more In many data analytical applications involving the comparison of means from several populations, analyses are adjusted by including one or more continuous variables in the model. Such an analysis is often called an Analysis of Covariance. In this study, we examine the effect of such an adjustment on the precision of inferences regarding the adjusted means and the interpretation of those means. We consider the variance of the difference between a pair of adjusted means and show that the variance is minimized when the mean of the covariate is the same in both groups. However, when the covariate means differ across groups, the additional term in the model can dominate the variance of the comparison. We investigate the break-even point for this comparison and under what condition that occurs. Finally, we demonstrate, with several data sets, how these results may be manifested in practice. here are a variety of analytical procedures that have been developed for use in comparing the perfo...
In agricultural education, both 4-H and FFA have identified leadership development as central to ... more In agricultural education, both 4-H and FFA have identified leadership development as central to their mission. Many Cooperative Extension Service and agricultural educators, members, and alumni think these organizations provide effective leadership programming. However, there is little research to support that viewpoint. The purpose of this study was to develop a valid, reliable scale to measure youth leadership life skills development. The first phase involved the conceptualization and operationalization of youth leadership life skills development (YLLSD). YLLSD was conceptualized as having seven sub-domains (Miller, 1976) and operationalized with 68 indicators. Each indicator used a four point Likert-type subscale. Face and content validity were assessed by a panel of experts. In the second phase, construct validity, reliability, and dimensionality were assessed. Data were collected during September and October, 1992, following the Dillman procedure. The target population was 6,3...
Conference on Applied Statistics in Agriculture, 1992
We investigate three alternative models for estimating the mean of a population using double samp... more We investigate three alternative models for estimating the mean of a population using double sampling survey techniques. One estimator was found in the range science literature (Cook and stubbendieck, 1986), another is the estimator presented by Cochran (1977). The third estimator uses method-ofmoments estimators with measurement error regression models. Simulation studies suggest that the measurement error model does not work well when the slope is appreciably different from unity. Delta method variance estimators of the measurement error model may give negative variance estimates under these circumstances. The other estimators have better small sample performance (both are approximately unbiased, and have similar variances), but the two estimators have very different estimated variances under some circumstances.
Due to a rapidly aging society, stagnating per capita income and rather stable prices, traditiona... more Due to a rapidly aging society, stagnating per capita income and rather stable prices, traditional economic analyses methods lost their power in the 1990s to predict future food product consumption in Japan. This study, in part, remedies this problem by projecting future consumption of selected products, using a cohort approach with economic factors tentatively set aside. Per capita consumption of individual household members by age was derived by incorporating family age composition into household data classified by age groups of household head (HH). Individual consumption estimates were decomposed into age, cohort and time effects, using the Nakamura's Bayesian cohort model. These effects were synthesized to predict per capita consumption in each population age cell in 2010 and 2020. Although some method refinement is warranted, the cohort approach proves a useful tool in improving prediction of future food product consumption and, combined with economic factors, may prove use...
Tests of theories that attempt to explain why individuals currently use drugs are widespread; how... more Tests of theories that attempt to explain why individuals currently use drugs are widespread; however, the theoretical examinations of abstention from drugs and the cessation of their use are rare. For its part, social learning theory has been supported consistently in its delineation of the process by which substance use is learned. We propose that cessation and abstention are also learned behavior, Using logistic regression analysis, we examine the ability of social learning variables to distinguish among abstainers, current users, and former users of illicit drugs within a sample of 1688 middle-and high-school students in two widely separated nonurban communities. Results indicate that social learning variables clearly distinguish abstainers from current users but are less able to distinguish former users and current users or former users from abstainers. The theoretical, research, and policy implications of these findings are examined in detail.
Broom snakeweed achene dispersal was monitored by placing surface-level traps outwards in the car... more Broom snakeweed achene dispersal was monitored by placing surface-level traps outwards in the cardinal directions from 12 plants and collecting the achenes weekly or biweekly from September 1993 until seeds were no longer retained by the plants after 42 wk. About 50% of the achenes dispersed between October and December. Especially high numbers of achenes were dislodged during periods of intense winter winds and rains, with 78% of the seed placed into the east tray and 86% falling within 50 cm of the parent plant. Achene production averaged 3,928 (± 1,146) per plant in 1993 and 2,036 (± 987) per plant in 1994. Achenes collected over time directly from the inflorescence and achenes stored in nylon packets on the soil surface averaged 82% viability during fall and winter. Achene viability declined rapidly in late spring, and few remained viable before the next seed crop. Greenhouse experiments compared the influence of water application interval and water amount on broom snakeweed ger...
Experiments were conducted to determine variation of in vitro microsclerotia production, pigmenta... more Experiments were conducted to determine variation of in vitro microsclerotia production, pigmentation, and growth of five Pyrenochaeta terrestris (Hans.) Gorenz, Walker, and Larson isolates from Texas and New Mexico. Isolates of P. terrestris, the causal agent of pink root rot, were placed on agar with lo-mm-long sections of sterile onion (Allium cepa L.) roots. Microsclerotia were present after 20 days at 20, 25, 27, or 32C, with the number of microsclerotia dependent on the isolate. Microsclerotia were absent at 35C. One isolate produced few microsclerotia at all temperatures. Optimum temperatures for growth on potato dextrose agar for the isolates tested were 25 and 27C. Pigment production in roots on agar varied depending on isolate and temperature. Three isolates produced high levels of pigment in onion roots at 15, 20, 25, and 27C. A New Mexico isolate produced significantly less visible pigment than the other New Mexico and Texas isolates. One isolate produced very little pig...
Conference on Applied Statistics in Agriculture, 1990
An FI interspecific hybrid onion (Allium cepa x A..:.. fistulosum) was backcrossed to the A..:.. ... more An FI interspecific hybrid onion (Allium cepa x A..:.. fistulosum) was backcrossed to the A..:.. cepa parent line under field conditions. The progeny of this cross were shown by electrophoretic protein analysis to be a mixture of BC l (the desired backcross) and F2 (A..:.. cepa x A..:.. fistulosum) x (A..:.. cepa x A..:.. fistulosum)individuals. This mixture of populations among the progeny render the usual X 2 test for independent segregation of loci invalid. F2 is used to denote progeny derived from either selfing of the Fl or from sib-crosses between two Fl individuals. A model for this mixed population has been developed; from this model the mixture fraction and crossover frequencies can be estimated using maximum likelihood.
... Bionomics of Cleonidius trivittatus (Coleoptera: Curculionidae): Native Biological Control of... more ... Bionomics of Cleonidius trivittatus (Coleoptera: Curculionidae): Native Biological Control of Purple Locoweed (Rosales: Fabaceae) ... Twenty-five1.0-m2 quadrats were sampled every 2 wk from 28 March to 26 September 1992 and every 3 wk from 15 April to 4 September 1993 to ...
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Papers by Dennis Clason