Description Implements diffusion map method of data parametrization,including creation and visual... more Description Implements diffusion map method of data parametrization,including creation and visualization of diffusion map,clustering with diffusion K-means and regression using adaptive regression model. Depends R (> = 2.4.0), scatterplot3d, igraph, Matrix
Journal of the American Society for Horticultural Science
Four categories of billbug (Sphenophorus parvulus Gyllenhal) resistance were identified and contr... more Four categories of billbug (Sphenophorus parvulus Gyllenhal) resistance were identified and contrasted in terms of anatomical, morphological, and physiological characteristics of 12 Kentucky bluegrass (Poa pratensis L.) cultivars. Discriminant analysis was used as a separatory procedure to determine the relative importance of these plant characteristics to observed billbug resistance and to construct a prediction procedure for potential billbug resistance classes. Variables measured from field-, controlled environment-, and greenhouse-grown plants were analyzed for the most biologically revealing characteristics of potential billbug resistance. Separatory discrimination indicated that cultivars exhibiting moderate and high billbug resistance had tougher tissue than tolerant or susceptible cultivars. Tolerant and highly resistant cultivars differed from those susceptible and moderately resistant by concealing billbug injury. Development of a predictive classification procedure was pr...
Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmon... more Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmonic least squares, ellipse-specific non-linear least squares, the direct method, geometric least squares or linear least squares.
Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmon... more Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmonic least squares, ellipse-specific non-linear least squares, or linear least squares.
The objective was to describe variability in prevalence, incidence, and duration of fecal sheddin... more The objective was to describe variability in prevalence, incidence, and duration of fecal shedding of naturally occurring E. coli O157:H7 by a group of feedlot cattle over time. One hundred steers, randomly assigned to 10 pens, were fed a high-concentrate finishing diet for 136 days (19 weeks). Rectal feces from each animal were tested for E. coli O157:H7 every week for 19 weeks. E. coli O157:H7 was recovered from each animal that completed the study and was detected from at least one animal every week. Average pen prevalence of cattle shedding E. coli O157:H7 varied significantly over time (P < 0.0001) and across pens (P < 0.0001), ranging from 1 to 80%. Pairwise comparisons of mean pen prevalence of E. coli O157:H7 between weeks and estimation of the predicted probability of an incident case of E. coli O157:H7 over time allowed the definition of three distinct phases—namely, the preepidemic, epidemic, and postepidemic periods. Average pen prevalence varied significantly over...
A multivariate factor analysis was used to explore associations among five measured energetic res... more A multivariate factor analysis was used to explore associations among five measured energetic responses for growing pigs as an improved analysis method to an analysis of predictions from an energetic mathematical model. The response variables were feed consumption, water vapor production, heat production, water consumption, and respiratory quotient. In one treatment, groups of four 36 kg pigs were housed in a calorimeter at temperatures cycling between a minimum of26°C to a maximum of40''C. In another treatment, groups of four 36 kg pigs were housed in a calorimeter at a constant temperature of 33°C. Three factors were extracted from the energetic data in each of the environmental treatments. These common factors described homeothermy, energy intake, energy retained and more clearly reflected the differences between the environments than any of the individual variables. Homeothermy was described by heat and water vapor production in the constant temperature treatment; while it was predominately described by water vapor production and water consumption in the cyclic temperature treatment. This factor represents heat loss as both sensible and latent heat in the constant temperature treatment but, primarily as latent heat in the cyclic temperature treatment. Cyclic temperatures caused higher than average homeothermy scores during the time of low energy retention and low energy intake scores (during peak temperatures), whereas constant temperatures caused high homeothermy scores during the time of high energy retention and high energy intake scores. Keywords, Factor analysis. Growing pigs. High ambient temperatures. Growth modeling. L ivestock environments are usually dynamic in nature. Within livestock housing, ambient temperature, air quality, and ventilation rate change with changes in outside temperature, animal heat production, and management practices (feeding, Hghting, manure removal). The total energetic responses of animals to cyclic or constant temperatures are difficult to evaluate due to the complex interplay of environmental, physiological and behavioral phenomena that are not readily observed. One way to assess such a response is to measure the many variables that are related to these mechanisms. In the case of energetics, such variables might be: heat production, heat loss, respiratory quotient, water vapor production, feed consumption, and water consumption. Data from such variables are often interrelated which indicates that some underlying commonality exists. Data with this characteristic may be simplified and better understood using a multivariate analysis such as a factor analysis. Previously, energetic variables for two temperature treatments were evaluated within a factorial experiment (Feddes and DeShazer, 1988). For each variable, a factorial analysis of variance was
Three experiments were conducted to evaluate the effect of different management strategies on bod... more Three experiments were conducted to evaluate the effect of different management strategies on body temperature of feedlot steers finished in the summer months. In Exp. 1, 24 crossbred steers were chosen to assess the effect of altered feed intake and feeding time on tympanic temperature (TT) response. Managed feeding (MF) treatments were applied for 22 d only and provided 1) ad libitum access to feed at 0800 (ADLIB), 2) feed at 1600 with amount adjusted so that no feed was available at 0800 (BKMGT), 3) feed at 1600 at 85% of predicted ad libitum levels (LIMFD). During heat stress conditions on d 20 to 22 of MF, LIMFD and BKMGT had lower (P < 0.05) TT than ADLIB from 2100 through 2400. A carryover effect of limit-feeding was evident during a severe heat episode (d 36 to 38) with LIMFD steers having lower (P < 0.05) TT than ADLIB. In Exp. 2, TT were obtained from 24 crossbred steers assigned to three treatments, consisting of no water
Autoregression-moving average (ARMA) models provide insight into many biological systems. One of ... more Autoregression-moving average (ARMA) models provide insight into many biological systems. One of the most difficult decisions in ARMA modeling is identifying the order of the model. Many procedures have been proposed. The purpose of this study was to compare Pandit and Wu\u27s multi-objective test criterion with Akaike\u27s information criterion and Schwartz\u27s Bayesian criterion, SBC. Several versions of the criteria were compared for 10 processes which were simulations of ARMA models ranging in order from (1,1) to (8,7). Batches of 100 realizations were generated for each model. The performance of the criteria varied depending on how closely a process complied with the assumptions, length of series and alpha levels chosen. The error variance and method of parameter estimation had no effect on the relative merits of the criteria. The proposed strategy uses Pandit and Wu\u27s (2p,2p-1) portfolio and SBC (or F-ratio, if sample size $\le$125) to identify a neighborhood for the model on the first pass. The portfolio is modified to include all models between adjacent primary models which define the neighborhood. In the second pass, a model is selected using SBC. Three classical time series were assessed by this strategy. The results compare favorably to those in the literature. The proposed strategy was utilized to identify a sensible heat loss model for non-laying hens. The ARMA(2,0) model which was selected for all four hens, explained 70 to 89% of the total variation. The proposed strategy was also used to identify a tympanic temperature model for steers housed in a constant thermoneutral environment. The ARMA(3,0) model was adequate for both animals in the study, although the model accounted for only 15 to 27% of the total variation. This dissertation is divided into four sections. The first contains a literature review of time series relative to dynamic systems. The second provides a comparison of order determination procedures and introduces a new strategy. The third describes the utilization of proposed strategy in modeling biological processes. The last section discusses various aspects in the construction of simulation software
H eat transfer from animals to the environment can be measured by both direct and indirect method... more H eat transfer from animals to the environment can be measured by both direct and indirect methods. Direct calorimetry, which utilizes physical measurement of an animal's sensible and latent heat loss, requires specially designed chambers with extensive thermal barriers and complex thermocouple circuitry or other complex thermal sensing systems. In indirect calorimetry, in contrast, the measurement of carbon dioxide (CO 2) and methane (CH 4 , for ruminants) production, oxygen (O 2) consumption, and urinary nitrogen (occasionally) are used to calculate the rate of total heat production (Brouwer, 1965). Indirect calorimeters are more flexible than direct calorimeters in the housing of animals, and can be easily modified to accommodate various species (Young et al., 1975). Indirect calorimetry also allows easy changes to the thermal environment; e.g., infrared heating, floor heating, air velocity, and is easily adapted for animal observation. In spite of the overall ease and flexibility of indirect calorimetry, however, the integration of low-cost, but precise, environmental control systems is problematic. The objectives of this study were: (1) to set up an indirect calorimeter with a within-chamber control system to monitor the humidity-temperature state points and to change them as necessary to offset heat and moisture production by the animal; and (2) to test the system to determine whether its average error at a variety of state points was acceptable for physiological studies with animals. MATERIALS AND METHODS ORIGINAL CHAMBERS Three identical environmental chambers were originally constructed by the Biological Systems Engineering Shop at the University of Nebraska-Lincoln for short-term calorimetry studies with medium-sized animals, such as young pigs (Xin and DeShazer, 1991), or turkeys (Xin et al., 1992). As described in detail in Xin (1989), the chambers have outside dimensions of 1 m wide, 1.5 m long, and 1.2 m high, and a total animal space of 1.2 m 3. The walls are double-sided plexiglass. For ease of moving and caring for animals, one end wall of the chamber is on a track; self-locking vertical clamp, located at each corner ensure a tight seal. The chambers were originally located in a larger room that was equipped with an AMICO air unit (Model No. AA-5460A, Parameter Generation and Control, Inc., Black Mountain, N.C.) and an insulated air intake duct system. Copper tubing had previously carried chamber air out, and solenoid valves allowed sequential analysis of CO 2 , O 2 , and moisture. Each chamber had a small heater that could be operated independently to create a thermal environment within the chamber, but there was no cooling mechanism; wet bulb temperatures (T wb) could be established only for all three chambers simultaneously by the AMICO unit (Xin, 1989). The AMICO unit could be set to precondition and deliver air at 20 to 50 standard L/min (sL/min). Intake air, monitored by a mass flow meter (Model No. HS-L100SF,
Temperature-humidity effects on physiological responses of tom turkeys were investigated using a ... more Temperature-humidity effects on physiological responses of tom turkeys were investigated using a twodimensional rotatable central composite design. Eight temperature-humidity combinations were evaluated from 23 to 40°C and 40 to 90% RH. Response surfaces for mean, variation, and slope of core body temperature, CO 2 production, and moisture production were used to assess level of stress at each of four ages. Temperature and humidity were approximately equal in their effects on physiological responses of 6-wk-old turkeys. Above 10 weeks of age, temperature decreased in relative significance as a stressor, and humidity appeared to be a more important factor in the birds' ability to maintain homeothermy.
Feelings of loneliness and isolation occur at various stages of life but are usually most intense... more Feelings of loneliness and isolation occur at various stages of life but are usually most intense during adolescence. Studies have shown that adolescent females experience loneliness to a greater degree than males do. This study was based on the hypothesis that low-income, single, adolescent mothers would report a greater degree of loneliness than 10 other selected populations. A 4-part questionnaire was administered to adolescent mothers receiving public assistance in a midwestern city. Statistical analyses showed that the loneliness scores of the low-income, single, adolescent mothers were higher than those of the other populations. Educational background, marital status of parents, accessibility of transportation, and income level were factors found to contribute significantly to feelings of loneliness in this sample. Several other factors were found to influence the loneliness scores.
Description Implements diffusion map method of data parametrization,including creation and visual... more Description Implements diffusion map method of data parametrization,including creation and visualization of diffusion map,clustering with diffusion K-means and regression using adaptive regression model. Depends R (> = 2.4.0), scatterplot3d, igraph, Matrix
Journal of the American Society for Horticultural Science
Four categories of billbug (Sphenophorus parvulus Gyllenhal) resistance were identified and contr... more Four categories of billbug (Sphenophorus parvulus Gyllenhal) resistance were identified and contrasted in terms of anatomical, morphological, and physiological characteristics of 12 Kentucky bluegrass (Poa pratensis L.) cultivars. Discriminant analysis was used as a separatory procedure to determine the relative importance of these plant characteristics to observed billbug resistance and to construct a prediction procedure for potential billbug resistance classes. Variables measured from field-, controlled environment-, and greenhouse-grown plants were analyzed for the most biologically revealing characteristics of potential billbug resistance. Separatory discrimination indicated that cultivars exhibiting moderate and high billbug resistance had tougher tissue than tolerant or susceptible cultivars. Tolerant and highly resistant cultivars differed from those susceptible and moderately resistant by concealing billbug injury. Development of a predictive classification procedure was pr...
Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmon... more Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmonic least squares, ellipse-specific non-linear least squares, the direct method, geometric least squares or linear least squares.
Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmon... more Description Fit, summarize and plot sinusoidal hysteretic processes using: two-step simple harmonic least squares, ellipse-specific non-linear least squares, or linear least squares.
The objective was to describe variability in prevalence, incidence, and duration of fecal sheddin... more The objective was to describe variability in prevalence, incidence, and duration of fecal shedding of naturally occurring E. coli O157:H7 by a group of feedlot cattle over time. One hundred steers, randomly assigned to 10 pens, were fed a high-concentrate finishing diet for 136 days (19 weeks). Rectal feces from each animal were tested for E. coli O157:H7 every week for 19 weeks. E. coli O157:H7 was recovered from each animal that completed the study and was detected from at least one animal every week. Average pen prevalence of cattle shedding E. coli O157:H7 varied significantly over time (P < 0.0001) and across pens (P < 0.0001), ranging from 1 to 80%. Pairwise comparisons of mean pen prevalence of E. coli O157:H7 between weeks and estimation of the predicted probability of an incident case of E. coli O157:H7 over time allowed the definition of three distinct phases—namely, the preepidemic, epidemic, and postepidemic periods. Average pen prevalence varied significantly over...
A multivariate factor analysis was used to explore associations among five measured energetic res... more A multivariate factor analysis was used to explore associations among five measured energetic responses for growing pigs as an improved analysis method to an analysis of predictions from an energetic mathematical model. The response variables were feed consumption, water vapor production, heat production, water consumption, and respiratory quotient. In one treatment, groups of four 36 kg pigs were housed in a calorimeter at temperatures cycling between a minimum of26°C to a maximum of40''C. In another treatment, groups of four 36 kg pigs were housed in a calorimeter at a constant temperature of 33°C. Three factors were extracted from the energetic data in each of the environmental treatments. These common factors described homeothermy, energy intake, energy retained and more clearly reflected the differences between the environments than any of the individual variables. Homeothermy was described by heat and water vapor production in the constant temperature treatment; while it was predominately described by water vapor production and water consumption in the cyclic temperature treatment. This factor represents heat loss as both sensible and latent heat in the constant temperature treatment but, primarily as latent heat in the cyclic temperature treatment. Cyclic temperatures caused higher than average homeothermy scores during the time of low energy retention and low energy intake scores (during peak temperatures), whereas constant temperatures caused high homeothermy scores during the time of high energy retention and high energy intake scores. Keywords, Factor analysis. Growing pigs. High ambient temperatures. Growth modeling. L ivestock environments are usually dynamic in nature. Within livestock housing, ambient temperature, air quality, and ventilation rate change with changes in outside temperature, animal heat production, and management practices (feeding, Hghting, manure removal). The total energetic responses of animals to cyclic or constant temperatures are difficult to evaluate due to the complex interplay of environmental, physiological and behavioral phenomena that are not readily observed. One way to assess such a response is to measure the many variables that are related to these mechanisms. In the case of energetics, such variables might be: heat production, heat loss, respiratory quotient, water vapor production, feed consumption, and water consumption. Data from such variables are often interrelated which indicates that some underlying commonality exists. Data with this characteristic may be simplified and better understood using a multivariate analysis such as a factor analysis. Previously, energetic variables for two temperature treatments were evaluated within a factorial experiment (Feddes and DeShazer, 1988). For each variable, a factorial analysis of variance was
Three experiments were conducted to evaluate the effect of different management strategies on bod... more Three experiments were conducted to evaluate the effect of different management strategies on body temperature of feedlot steers finished in the summer months. In Exp. 1, 24 crossbred steers were chosen to assess the effect of altered feed intake and feeding time on tympanic temperature (TT) response. Managed feeding (MF) treatments were applied for 22 d only and provided 1) ad libitum access to feed at 0800 (ADLIB), 2) feed at 1600 with amount adjusted so that no feed was available at 0800 (BKMGT), 3) feed at 1600 at 85% of predicted ad libitum levels (LIMFD). During heat stress conditions on d 20 to 22 of MF, LIMFD and BKMGT had lower (P < 0.05) TT than ADLIB from 2100 through 2400. A carryover effect of limit-feeding was evident during a severe heat episode (d 36 to 38) with LIMFD steers having lower (P < 0.05) TT than ADLIB. In Exp. 2, TT were obtained from 24 crossbred steers assigned to three treatments, consisting of no water
Autoregression-moving average (ARMA) models provide insight into many biological systems. One of ... more Autoregression-moving average (ARMA) models provide insight into many biological systems. One of the most difficult decisions in ARMA modeling is identifying the order of the model. Many procedures have been proposed. The purpose of this study was to compare Pandit and Wu\u27s multi-objective test criterion with Akaike\u27s information criterion and Schwartz\u27s Bayesian criterion, SBC. Several versions of the criteria were compared for 10 processes which were simulations of ARMA models ranging in order from (1,1) to (8,7). Batches of 100 realizations were generated for each model. The performance of the criteria varied depending on how closely a process complied with the assumptions, length of series and alpha levels chosen. The error variance and method of parameter estimation had no effect on the relative merits of the criteria. The proposed strategy uses Pandit and Wu\u27s (2p,2p-1) portfolio and SBC (or F-ratio, if sample size $\le$125) to identify a neighborhood for the model on the first pass. The portfolio is modified to include all models between adjacent primary models which define the neighborhood. In the second pass, a model is selected using SBC. Three classical time series were assessed by this strategy. The results compare favorably to those in the literature. The proposed strategy was utilized to identify a sensible heat loss model for non-laying hens. The ARMA(2,0) model which was selected for all four hens, explained 70 to 89% of the total variation. The proposed strategy was also used to identify a tympanic temperature model for steers housed in a constant thermoneutral environment. The ARMA(3,0) model was adequate for both animals in the study, although the model accounted for only 15 to 27% of the total variation. This dissertation is divided into four sections. The first contains a literature review of time series relative to dynamic systems. The second provides a comparison of order determination procedures and introduces a new strategy. The third describes the utilization of proposed strategy in modeling biological processes. The last section discusses various aspects in the construction of simulation software
H eat transfer from animals to the environment can be measured by both direct and indirect method... more H eat transfer from animals to the environment can be measured by both direct and indirect methods. Direct calorimetry, which utilizes physical measurement of an animal's sensible and latent heat loss, requires specially designed chambers with extensive thermal barriers and complex thermocouple circuitry or other complex thermal sensing systems. In indirect calorimetry, in contrast, the measurement of carbon dioxide (CO 2) and methane (CH 4 , for ruminants) production, oxygen (O 2) consumption, and urinary nitrogen (occasionally) are used to calculate the rate of total heat production (Brouwer, 1965). Indirect calorimeters are more flexible than direct calorimeters in the housing of animals, and can be easily modified to accommodate various species (Young et al., 1975). Indirect calorimetry also allows easy changes to the thermal environment; e.g., infrared heating, floor heating, air velocity, and is easily adapted for animal observation. In spite of the overall ease and flexibility of indirect calorimetry, however, the integration of low-cost, but precise, environmental control systems is problematic. The objectives of this study were: (1) to set up an indirect calorimeter with a within-chamber control system to monitor the humidity-temperature state points and to change them as necessary to offset heat and moisture production by the animal; and (2) to test the system to determine whether its average error at a variety of state points was acceptable for physiological studies with animals. MATERIALS AND METHODS ORIGINAL CHAMBERS Three identical environmental chambers were originally constructed by the Biological Systems Engineering Shop at the University of Nebraska-Lincoln for short-term calorimetry studies with medium-sized animals, such as young pigs (Xin and DeShazer, 1991), or turkeys (Xin et al., 1992). As described in detail in Xin (1989), the chambers have outside dimensions of 1 m wide, 1.5 m long, and 1.2 m high, and a total animal space of 1.2 m 3. The walls are double-sided plexiglass. For ease of moving and caring for animals, one end wall of the chamber is on a track; self-locking vertical clamp, located at each corner ensure a tight seal. The chambers were originally located in a larger room that was equipped with an AMICO air unit (Model No. AA-5460A, Parameter Generation and Control, Inc., Black Mountain, N.C.) and an insulated air intake duct system. Copper tubing had previously carried chamber air out, and solenoid valves allowed sequential analysis of CO 2 , O 2 , and moisture. Each chamber had a small heater that could be operated independently to create a thermal environment within the chamber, but there was no cooling mechanism; wet bulb temperatures (T wb) could be established only for all three chambers simultaneously by the AMICO unit (Xin, 1989). The AMICO unit could be set to precondition and deliver air at 20 to 50 standard L/min (sL/min). Intake air, monitored by a mass flow meter (Model No. HS-L100SF,
Temperature-humidity effects on physiological responses of tom turkeys were investigated using a ... more Temperature-humidity effects on physiological responses of tom turkeys were investigated using a twodimensional rotatable central composite design. Eight temperature-humidity combinations were evaluated from 23 to 40°C and 40 to 90% RH. Response surfaces for mean, variation, and slope of core body temperature, CO 2 production, and moisture production were used to assess level of stress at each of four ages. Temperature and humidity were approximately equal in their effects on physiological responses of 6-wk-old turkeys. Above 10 weeks of age, temperature decreased in relative significance as a stressor, and humidity appeared to be a more important factor in the birds' ability to maintain homeothermy.
Feelings of loneliness and isolation occur at various stages of life but are usually most intense... more Feelings of loneliness and isolation occur at various stages of life but are usually most intense during adolescence. Studies have shown that adolescent females experience loneliness to a greater degree than males do. This study was based on the hypothesis that low-income, single, adolescent mothers would report a greater degree of loneliness than 10 other selected populations. A 4-part questionnaire was administered to adolescent mothers receiving public assistance in a midwestern city. Statistical analyses showed that the loneliness scores of the low-income, single, adolescent mothers were higher than those of the other populations. Educational background, marital status of parents, accessibility of transportation, and income level were factors found to contribute significantly to feelings of loneliness in this sample. Several other factors were found to influence the loneliness scores.
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Papers by Anne Parkhurst