Based on the most recent census data, watermelon is the second largest planted vegetable crop in ... more Based on the most recent census data, watermelon is the second largest planted vegetable crop in Kentucky (USDA, 2013). Watermelon is a favorite summertime treat and has been increasing in acreage as have vegetables as a whole in the state (Snell et al., 2013). It is both marketed directly and via wholesale with production scattered throughout the state. Some areas of concentrated watermelon production include Allen,
Journal of Exposure Science & Environmental Epidemiology, 2008
The US EPA Worker Protection Standard requires pesticide safety training for farmworkers. Combine... more The US EPA Worker Protection Standard requires pesticide safety training for farmworkers. Combined with re-entry intervals, these regulations are designed to reduce pesticide exposure. Little research has been conducted on whether additional steps may reduce farmworker exposure and the potential for take-home exposure to their families. We conducted an intervention with 44 strawberry harvesters (15 control and 29 intervention group members) to determine whether education, encouragement of handwashing, and the use of gloves and removable coveralls reduced exposure. Post-intervention, we collected foliage and urine samples, as well as hand rinse, lower-leg skin patch, and clothing patch samples. Post-intervention loading of malathion on hands was lower among workers who wore gloves compared to those who did not (median ¼ 8.2 vs. 777.2 mg per pair, respectively (Po0.001)); similarly, median MDA levels in urine were lower among workers who wore gloves (45.3 vs. 131.2 mg/g creatinine, Po0.05). Malathion was detected on clothing (median ¼ 0.13 mg/cm 2), but not on skin. Workers who ate strawberries had higher malathion dicarboxylic acid levels in urine (median ¼ 114.5 vs. 39.4 mg/g creatinine, Po0.01). These findings suggest that wearing gloves reduces pesticide exposure to workers contacting strawberry foliage containing dislodgeable residues. Additionally, wearing gloves and removing work clothes before returning home could reduce transport of pesticides to worker homes. Behavioral interventions are needed to reduce consumption of strawberries in the field.
The presence of 7-epi zingiberene in wild tomatoes has been associated with arthropod resistance.... more The presence of 7-epi zingiberene in wild tomatoes has been associated with arthropod resistance. Consequently, tomato breeders are attempting to introgress 7-epi zingiberene from wild to cultivated tomato requiring quantification of zingiberene. 7-Epi zingiberene likely absorbs UV light due to its conjugated double bonds and others have claimed that measurement of absorbance at 270 nm of tomato leaflet washes can be used to quantify zingiberene. However, this claim has never been critically evaluated. We initially evaluated this claim in an interspecific hybrid tomato generation that was segregating widely for zingiberene. Results indicated that the method does not obey the Beer–Lambert law. Consequently, we examined in detail aspects of the UV-absorbance of isolated zingiberenoids and leaflet washes obtained from parents and interspecific generations that were segregating for 7-epi zingiberene. Results indicated that isolated zingiberenoids, as well as leaflet washes containing zi...
The medicinal plant Salvia miltiorrhiza produces various tanshinone diterpenoids that have pharma... more The medicinal plant Salvia miltiorrhiza produces various tanshinone diterpenoids that have pharmacological activities such as vasorelaxation, against ischemia-reperfusion injury, and antiarrhythmic effects. Their biosynthesis is initiated from the general diterpenoid precursor (E,E,E)-geranylgeranyl diphosphate by sequential reactions catalyzed by copalyl diphosphate synthase (CPS) and kaurene synthase-like (KSL) cyclases. Here is reported characterization of these enzymatic families from S. miltiorrhiza, which has led to the identification of novel pathways, including roles for separate CPSs in tanshinone production in roots versus aerial tissues (SmCPS1 and SmCPS2, respectively), as well as the novel production of ent-13-epi-manoyl oxide by SmCPS4 and SmKSL2 in floral sepals. The conserved SmCPS5 is involved in gibberellin plant hormone biosynthesis. Down-regulation of SmCPS1 by RNAi resulted in substantial reduction of tanshinones, and metabolomics analysis revealed 21 potential ...
Using a one-dimensional model, we explore the ability of machine learning to approximate the non-... more Using a one-dimensional model, we explore the ability of machine learning to approximate the non-interacting kinetic energy density functional of diatomics. This nonlinear interpolation between Kohn-Sham reference calculations can (i) accurately dissociate a diatomic, (ii) be systematically improved with increased reference data and (iii) generate accurate self-consistent densities via a projection method that avoids directions with no data. With relatively few densities, the error due to the interpolation is smaller than typical errors in standard exchange-correlation functionals.
Raffinose family oligosaccharides (RFOs) have been implicated in mitigating the effects of enviro... more Raffinose family oligosaccharides (RFOs) have been implicated in mitigating the effects of environmental stresses on plants.
Machine learning is used to approximate density functionals. For the model problem of the kinetic... more Machine learning is used to approximate density functionals. For the model problem of the kinetic energy of noninteracting fermions in 1D, mean absolute errors below 1 kcal/mol on test densities similar to the training set are reached with fewer than 100 training densities. A predictor identifies if a test density is within the interpolation region. Via principal component analysis, a projected functional derivative finds highly accurate self-consistent densities. The challenges for application of our method to real electronic structure problems are discussed.
Journal of Environmental Science and Health, Part B, 2004
The adsorption and mobility of pyrethrins (Pys), the major insecticidal components obtained from ... more The adsorption and mobility of pyrethrins (Pys), the major insecticidal components obtained from the pyrethrum daisy Tanacetum cinerariifolium, and piperonyl butoxide (PBO), a pyrethrum synergist, were determined in soil using batch-equilibrium and reverse-phase thin-layer chromatographic techniques. Two soil management practices were used, soil mixed with yard waste compost (COM) at 50 t acre(-1) on dry weight basis and no-mulch (NM) bare soil. Adsorption isotherm experiments were carried out using known concentrations of Pys (Py-I and Py-II) and PBO mixed with known amounts of COM or NM soil at constant temperature and pressure until equilibrium was attained. Pys and PBO in soil extracts were purified and concentrated using solid-phase extraction cartridges containing C18-octadecyl bonded silica. Pys and PBO residues were quantified using a high-performance liquid chromatograph equipped with a UV detector. Adsorption studies showed that compost amended soil adsorbed more Pys and PBO than native (NM) soil. Py-I adsorption was greater than Py-II and PBO. Adsorption of Pys and PBO to humic and fulvic acids was also studied by reverse-phase thin layer chromatography (RPTLC). Results indicated that humic acid, a significant component of organic matter, reduced Pys and PBO mobility. Pys and PBO mobility decreased as the concentration of humic acid in the mobile phase increased.
Based on the most recent census data, watermelon is the second largest planted vegetable crop in ... more Based on the most recent census data, watermelon is the second largest planted vegetable crop in Kentucky (USDA, 2013). Watermelon is a favorite summertime treat and has been increasing in acreage as have vegetables as a whole in the state (Snell et al., 2013). It is both marketed directly and via wholesale with production scattered throughout the state. Some areas of concentrated watermelon production include Allen,
Journal of Exposure Science & Environmental Epidemiology, 2008
The US EPA Worker Protection Standard requires pesticide safety training for farmworkers. Combine... more The US EPA Worker Protection Standard requires pesticide safety training for farmworkers. Combined with re-entry intervals, these regulations are designed to reduce pesticide exposure. Little research has been conducted on whether additional steps may reduce farmworker exposure and the potential for take-home exposure to their families. We conducted an intervention with 44 strawberry harvesters (15 control and 29 intervention group members) to determine whether education, encouragement of handwashing, and the use of gloves and removable coveralls reduced exposure. Post-intervention, we collected foliage and urine samples, as well as hand rinse, lower-leg skin patch, and clothing patch samples. Post-intervention loading of malathion on hands was lower among workers who wore gloves compared to those who did not (median ¼ 8.2 vs. 777.2 mg per pair, respectively (Po0.001)); similarly, median MDA levels in urine were lower among workers who wore gloves (45.3 vs. 131.2 mg/g creatinine, Po0.05). Malathion was detected on clothing (median ¼ 0.13 mg/cm 2), but not on skin. Workers who ate strawberries had higher malathion dicarboxylic acid levels in urine (median ¼ 114.5 vs. 39.4 mg/g creatinine, Po0.01). These findings suggest that wearing gloves reduces pesticide exposure to workers contacting strawberry foliage containing dislodgeable residues. Additionally, wearing gloves and removing work clothes before returning home could reduce transport of pesticides to worker homes. Behavioral interventions are needed to reduce consumption of strawberries in the field.
The presence of 7-epi zingiberene in wild tomatoes has been associated with arthropod resistance.... more The presence of 7-epi zingiberene in wild tomatoes has been associated with arthropod resistance. Consequently, tomato breeders are attempting to introgress 7-epi zingiberene from wild to cultivated tomato requiring quantification of zingiberene. 7-Epi zingiberene likely absorbs UV light due to its conjugated double bonds and others have claimed that measurement of absorbance at 270 nm of tomato leaflet washes can be used to quantify zingiberene. However, this claim has never been critically evaluated. We initially evaluated this claim in an interspecific hybrid tomato generation that was segregating widely for zingiberene. Results indicated that the method does not obey the Beer–Lambert law. Consequently, we examined in detail aspects of the UV-absorbance of isolated zingiberenoids and leaflet washes obtained from parents and interspecific generations that were segregating for 7-epi zingiberene. Results indicated that isolated zingiberenoids, as well as leaflet washes containing zi...
The medicinal plant Salvia miltiorrhiza produces various tanshinone diterpenoids that have pharma... more The medicinal plant Salvia miltiorrhiza produces various tanshinone diterpenoids that have pharmacological activities such as vasorelaxation, against ischemia-reperfusion injury, and antiarrhythmic effects. Their biosynthesis is initiated from the general diterpenoid precursor (E,E,E)-geranylgeranyl diphosphate by sequential reactions catalyzed by copalyl diphosphate synthase (CPS) and kaurene synthase-like (KSL) cyclases. Here is reported characterization of these enzymatic families from S. miltiorrhiza, which has led to the identification of novel pathways, including roles for separate CPSs in tanshinone production in roots versus aerial tissues (SmCPS1 and SmCPS2, respectively), as well as the novel production of ent-13-epi-manoyl oxide by SmCPS4 and SmKSL2 in floral sepals. The conserved SmCPS5 is involved in gibberellin plant hormone biosynthesis. Down-regulation of SmCPS1 by RNAi resulted in substantial reduction of tanshinones, and metabolomics analysis revealed 21 potential ...
Using a one-dimensional model, we explore the ability of machine learning to approximate the non-... more Using a one-dimensional model, we explore the ability of machine learning to approximate the non-interacting kinetic energy density functional of diatomics. This nonlinear interpolation between Kohn-Sham reference calculations can (i) accurately dissociate a diatomic, (ii) be systematically improved with increased reference data and (iii) generate accurate self-consistent densities via a projection method that avoids directions with no data. With relatively few densities, the error due to the interpolation is smaller than typical errors in standard exchange-correlation functionals.
Raffinose family oligosaccharides (RFOs) have been implicated in mitigating the effects of enviro... more Raffinose family oligosaccharides (RFOs) have been implicated in mitigating the effects of environmental stresses on plants.
Machine learning is used to approximate density functionals. For the model problem of the kinetic... more Machine learning is used to approximate density functionals. For the model problem of the kinetic energy of noninteracting fermions in 1D, mean absolute errors below 1 kcal/mol on test densities similar to the training set are reached with fewer than 100 training densities. A predictor identifies if a test density is within the interpolation region. Via principal component analysis, a projected functional derivative finds highly accurate self-consistent densities. The challenges for application of our method to real electronic structure problems are discussed.
Journal of Environmental Science and Health, Part B, 2004
The adsorption and mobility of pyrethrins (Pys), the major insecticidal components obtained from ... more The adsorption and mobility of pyrethrins (Pys), the major insecticidal components obtained from the pyrethrum daisy Tanacetum cinerariifolium, and piperonyl butoxide (PBO), a pyrethrum synergist, were determined in soil using batch-equilibrium and reverse-phase thin-layer chromatographic techniques. Two soil management practices were used, soil mixed with yard waste compost (COM) at 50 t acre(-1) on dry weight basis and no-mulch (NM) bare soil. Adsorption isotherm experiments were carried out using known concentrations of Pys (Py-I and Py-II) and PBO mixed with known amounts of COM or NM soil at constant temperature and pressure until equilibrium was attained. Pys and PBO in soil extracts were purified and concentrated using solid-phase extraction cartridges containing C18-octadecyl bonded silica. Pys and PBO residues were quantified using a high-performance liquid chromatograph equipped with a UV detector. Adsorption studies showed that compost amended soil adsorbed more Pys and PBO than native (NM) soil. Py-I adsorption was greater than Py-II and PBO. Adsorption of Pys and PBO to humic and fulvic acids was also studied by reverse-phase thin layer chromatography (RPTLC). Results indicated that humic acid, a significant component of organic matter, reduced Pys and PBO mobility. Pys and PBO mobility decreased as the concentration of humic acid in the mobile phase increased.
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Papers by John Snyder