R-3 Repository :: Browsing by Author "Sass, Ronald L."

Browsing by Author "Sass, Ronald L."

Now showing 1 - 20 of 23

A new approach to evaluate regional methane emission from irrigated rice paddies: Combining process study, modeling and remote sensing into GIS
(2000) Ding, Aiju; Sass, Ronald L.
A large seasonal variation in methane emission from Texas rice fields was observed in most of the growing seasons from 1989 through 1997. In general, the pattern showed small fluxes in the early season of cultivation and reached maximum at post-heading time, then declined and stopped after fields were drained. The amount of methane emission positively relates to the aboveground biomass, the number of effective stems and tillers, and nitrogen addition. The day-to-day pattern of methane emissions was similar among all cultivars. The seasonal total methane emission shows a significant positive correlation with post-heading plant height. The total methane emission from Texas rice fields was estimated as 33.25 x 109 g in 1993, ranging from 25.85 x 109 g/yr to 40.65 x 109 g/yr. A mitigation technique was developed to obtain both high yield and less methane emission from Texas rice fields. A new approach was also developed to evaluate regional to large-scale methane emission from irrigated rice paddies. By combining modeling, ground truth information and remote sensing into a Geographic Information System (GIS)---a computer based system, the seasonal methane emission from a large area can be calculated efficiently and more accurately. The methodology was tested at the Richmond Irrigation District (RID) site in Texas. The average daily methane emission varied from field to field and even within a single field. The calculated seasonal total methane emission from RID rice fields was as low as 3.34 x 108 g CH4 in 1996 and as high as 7.80 x 108 g CH4 in 1998. To support the application of the estimation method in a worldwide study, an algorithm describing the mapping of irrigated rice paddies from Landsat TM data was demonstrated. The accuracy in 1998-supervised classification approached 95% when cloud cover was taken into account. Model uncertainty and data availability are the two major potential problems in worldwide application of the new approach. A potential alternative model is proposed which allows estimation of regional methane emission from rice plant height.
A study on methane emission from rice paddy fields and the nonstructural carbohydrates in rice plants
(1993) Wang, Yongbing; Sass, Ronald L.; Fisher, Frank M.
A dynamic process of the nonstructural carbohydrate translocation in rice plants is presented based on observation during one growing season. Differing amounts of nonstructural carbohydrates might be lost through rice plants due to the experimental plant manipulation. Relative to the CH$\sb4$ flux from the area of normal plants, significant increases in methane emission were observed in the area of manipulated plants. It is proposed that due to the experimental plant manipulation, more organic deposition entered the soil through rice plants than that under normal condition and, the lost nonstructural carbohydrate resulted in methane emission through the anaerobic methanogenesis in the rice field.
Assessing the relationship between soil reduction and methane emission in Texas rice fields
(1995) Lewis, Sandra Tracey; Sass, Ronald L.
Reduction processes and methane emissions have been observed in six rice fields along a sand-clay-silt gradient for one growing season. Variations in reduction processes occurred by depth and upon field draining, as well as among fields of differing soil sand content. Analysis at four 2.5 cm-intervals revealed that greater microbial activity appears to be occurring close to the surface of the soil, and decreases with depth. This may be due to greater substrate availability through decomposition of organic matter from roots and dead plant material at that location. Also, it was observed that the re-entry of oxygen upon field draining decreases the amount of reduction occurring, as well as the levels of methane emitted. In this study, greater amounts of emitted methane were measured from the sandy soil extreme. Reduction processes, however, were found to be similar in both clayey and sandy soils.
Conflict over male production in stingless bees
(2002) Toth, Eva; Sass, Ronald L.
Although social hymenopteran colonies show a high level of cooperation among their members, colony members can have conflicts among themselves as well. One of these intra-colonial conflicts is who produces the males. I studied the resolution of conflict in stingless bees, a species-rich group with a tropical distribution. In the majority of stingless bee species both workers and queens are able to produce males. Therefore intracolonial conflict over male production is predicted. Because stingless bee queens mate only once, workers are more related to their own and to each other's sons than to the sons of the queen. Thus on genetic grounds, worker production of males is expected. However, workers might not reproduce if the costs of reproduction are high, or if the queen is able to suppress workers. The decision could have been made in the bygone times and the current pattern does not serve adaptive functions at the present. To test my predictions of conflict over male production I looked at three levels: within colonies, within species, and between species. On the colony and species level, I hypothesized that current conflict is expressed by behavioral antagonism between the workers and their queen. Furthermore, I predicted behavioral conflict to be higher in the periods when males are produced compared to periods with only female production. On the level of comparison between species I expected more signs of conflict in species where both workers and queen produce males than in species where males are all queen derived. The conclusions of this study concerning conflict over male production in stingless bees are: (1) Genetic tools confirmed that workers reproduce in some, but not in other species. (2) The costs involved with worker reproduction could explain why in some species workers reproduce and in others not. (3) There is not only a variance of worker reproduction between, but also within species. Demographical factors might be essential determining the amount of worker reproduction within species. (4) The pattern of worker reproduction could be explained by costs although phylogenetic relationships could explain the pattern also.
Development and Climate Factors to Consider for the Successful Future of the Addicks Reservoir and Dam
(James A. Baker III Institute for Public Policy, 2011) Sass, Ronald L.; James A. Baker III Institute for Public Policy
Developmental changes in mechanosensory circuits during metamorphosis of the hawkmoth
(1988) Linn, David Martin, Jr; Sass, Ronald L.
In the hawkmoth, Manduca sexta, many behaviors are partially or fully functional but are actively suppressed prior to normal expression. The pupal gin-trap reflex is such a behavior and its development prior to repression was examined both behaviorally and physiologically. Behavioral responses similar to the pupae were observed in the latter stages of wandering. These responses were rapid lateral flexions and rotary abdomenal movements. The responses differed from the pupal responses in that the flexions were not segment-specific and the rotary movements were not confined to the abdomen as in the pupa. Physiological responses similar in amplitude to the pupa were also observed in the motorneurons during this stage. The responses also resembled the pupal by way of rapid depolarizations followed by inhibition. The responses differed by being non-segment-specific and repetitive in nature during a stimulation period. The results suggest the reflex is at least partially functional prior to pupation.
Differential scanning calorimetry studies of various fluorinated plastics
(1979) Pederson, John Alvin; Margrave, John L.; Glass, Graham P.; Sass, Ronald L.
Partial fluorination of various hydrocarbon plastics have been done at different temperatures for different lengths of time. By visual inspection of the surface, polypropylene received the most effective surface fluorination while polyethylene received somewhat less effective fluorination. Thickness of the plastic and position in the cylinder were two parameters to be considered for optimum fluorination. The du Pont differential scanning calorimeter was used to measure the effectiveness of the Fluorokoting against thermal oxidation. Air was used for the atmosphere, and two heating rates were utilized: 5° and 1° per minute. Slopes of the curves were compared for all plastics. Areas(heat evolved) were considered for polypropylene only. Results show that polypropylene had the most effective fluorokoting while the polyethylenes were less effective. This observation confirmed the results of the visual inspection of the surface. The DSC was also utilized in the Department of Transportation project. The parameters of interest were the amount of heat released by the compound and the initial onset temperature. Other surface properties that can be examined are contact angles and "smoothness." The contact angle with water decreased initially with fluorination, but then increased with increasing time of fluorination. Also, the higher the temperature of fluorination, the larger the contact angle. A scanning electron microscope was used to visually examine the surface of one of the fluorinated samples of polypropylene as compared to the surface of unfluorinated polypropylene. Surface differences were easily detected in these samples by photographs of magnifications of 2,x.
DNA damage and cell lethality by photodynamically-produced oxygen radicals
(1989) Burch, Paula Ellen; Sass, Ronald L.
Synthetic dyes, including thiazines, acridines, xanthenes, and a phenazine, were used as models for studying the photodynamic effect. In the presence of physiological reductants, the illuminated dyes produced superoxide (O$\sb2\sp-$), hydrogen peroxide (H$\sb2$O$\sb2$), and hydroxyl free radical (OH). Suitable reductants included NADH, glutathione, GMP, cysteine, tryptophan, and tyrosine. The production of OH$\cdot$ was dependent on chelated iron or on copper. Effective iron chelators included EDTA, DTPA, dipyridyl, and phenanthroline, and biologically significant compounds such as ATP, ADP, succinate, citrate, and DNA. DNA intercalation of the dyes did not prevent oxidization of NADH or the production of O$\sb2\sp-$ or OH$\cdot$. Hydroxyl radical scavengers competed effectively in the assays for the OH$\cdot$. While in the Haber-Weiss reaction superoxide reduces iron, which is oxidized by H$\sb2$O$\sb2$ to produce OH$\cdot$, excited state reduced dyes appeared capable of reducing the iron, so that SOD was only partially inhibitory of OH$\cdot$ production. Catalase prevented production of OH$\cdot$. Similar results were found for substrates and metals in an assay of single strand scission of DNA mediated by the dyes. Amounts of strand scission seen were dependent on concentrations of iron or dye. Cysteine, NADH, GTP, dGMP, tryptophan, and tyrosine were all able to provide electrons for the strand scission reaction. Furthermore, the single strand scission of DNA by the dyes was prevented by scavengers of O$\sb2\sp-$, H$\sb2$O$\sb2$ or OH$\cdot$ which are poor scavengers for singlet oxygen ($\sp1$O$\sb2$), and substitution of deuterium oxide for water, which exacerbates any damage produced by $\sp1$O$\sb2$, did not increase damage. The physiological reductant glutathione in E. coli was depleted by exposure to illuminated dye. Lethality of the dyes was reduced by enhanced levels of catalase or endonulcease IV provided by plasmid-coded genes, indicating that H$\sb2$O$\sb2$ is an important mediator of toxicity and that DNA is an important target, while OH$\cdot$ scavengers prevented kill, indicating that the OH$\cdot$ is also an important mediator of phototoxicity. Finally, DNA damage in vivo was reduced by an OH$\cdot$ scavenger. In conclusion, toxicity in the photodynamic effect is mediated by reduced oxygen species, particularly OH$\cdot$, and DNA damage probably underlies this toxicity.
Enrichment of a high rate tetrachloroethene dechlorinating culture: Role of electron donor
(1997) Carr, Cynthia Schmidt; Bedient, Philip B.; Sass, Ronald L.
A high rate tetrachloroethene (PCE) dechlorinating culture was enriched under methanogenic conditions that was able to dechlorinate 86 mg/L PCE to cis-1,2-DCE and vinyl chloride within 15 hours. In subsequent studies, the influence of electron donor on the ability to sustain PCE dechlorination was investigated in upflow columns inoculated with either the PCE enrichment culture or a (1:1) mixture of the enrichment culture and soil from contaminated field sites. One column from each inoculum subset was fed 34 milliequivalents of lactate, methanol, or hydrogen as electron donor and 5 mg/L PCE every four days. PCE was dechlorinated to primarily vinyl chloride in all six columns. Rates of PCE dechlorination were found to be similar with regard to inoculum, and did not vary extensively between electron donors. High hydrogen partial pressures were not found to be inhibitory to dechlorination.
Frequently Asked Questions: Climate Change
(James A. Baker III Institute for Public Policy, 2009) Sass, Ronald L.; James A. Baker III Institute for Public Policy
Functional connections between motion detectors in the optic nerve and connective of the crayfish
(1980) Martel, Michael Lee; Glantz, Raymon M.; Sass, Ronald L.; Troelstra, Arne
Results are reported here from experiments in which single unit neural activity was recorded simultaneously from the optic nerve and connective of the crayfish Procombarus clarkli to study functional connections between units responding to movement in visual space. The single unit data was analyzed through computer generated plots of poststimulus time histograms, interspike interval histograms, autocorrelation plots, joint peristimulus time histograms and normal and shifted crosscorrelation plots. In three experiments, discussed here in detail, evidence was obtained for strong functional connections between optic nerve motion detectors and connective motion detectors. In two other experiments, evidence was obtained for strong functional connections between the connective motion detectors and units in the other two classes of crayfish optic nerve visual units: the sustaining units and the dimming units.
Grus americana and a Texas River: A Case for Environmental Justice
(James A. Baker III Institute for Public Policy, 2010) Sass, Ronald L.; James A. Baker III Institute for Public Policy
Intervarietal differences of methane emission related to plant parameters in irrigated rice cultivation
(1995) Willis, Cylette Raucene; Sass, Ronald L.
Field and laboratory experiments were conducted with the following ten cultivars of rice: Lebonnet, Lemont, Dawn, Katy, Della, IR36, Mars, Brazos, Labelle and Jasmine. For each variety, components of biomass, root porosity and methane emission were observed throughout the entire growing season and yield was determined at harvest. Methane emission differed among cultivars by as much as a factor of 2.4 and resulted in two distinct emission groups. Significant differences were also found for biomass among cultivars, although these differences did not coincide with the differences that were observed for emission among cultivars. Methane emission correlated strongly with aboveground live vegetative biomass within most varieties until heading and among cultivars within emission groups to heading. Emissions showed less correlation with biomass during ripening and may have been affected by other factors within the system at this time. Methane emission appeared to be consistently proportional to grain production among cultivars, when determined per gram biomass, and may be related through processes of carbohydrate partitioning. Root porosity did not appear to be associated with observed differences or trends in methane emission.
Iodide transport in black lipid membranes
(1973) Heuer, Sharon Sue Beisemeier; Sass, Ronald L.
A study of iodide transport in the iodine-iodide-black lipid membrane system was carried out. Conductance data suggests that the transport process is first order with respect to both the iodine and iodide concentrations. To account for this and other experimental observations, a mechanism of iodide transport is postulated in which the formation of I is the rate determining step. The antithyroid agents, potassium thiocyanate, 6-n-propyl-2thiouracil, and 2-L-thiolhistidine were observed to inhibit iodide transport. It is thought that potassium thiocyanate acts in competition with iodide for iodine complex formation. The two other thio-compounds, being much more effective inhibitors, are believed to inhibit transport by reducing the iodine in the system. Perchlorate, also a well known goitrogen, was observed to have no effect on iodide transport. It is postulated that it affects thyroidal iodide metabolism in steps subsequent to iodide transport, perhaps by interaction with iodide peroxidase. In addition, histidine was shown to affect transport in a manner similar to thiocyanate. As a result, it is suggested that histidine may form a complex with iodine. Bromide, which has no antithyroid effect, was observed to be transported by iodine almost as easily as iodide. The proposed mechanism of iodide transport is used to explain the mode of action of the antithyroid agents on thyroidal iodide transport and is shown to account for many of the experimental and clinical observations in the literature. Further experiments are suggested to substantiate the proposed mechanism.
Methane emission from irrigated rice cultivation: Quantities, models and practice
(1997) Huang, Yao; Sass, Ronald L.
Three experiments focused on the contribution of rice productivity to methane emission were conducted in Texas flooded rice paddy soils during 1994-95 growing seasons. Measurements of methane emission from different rice paddy soils during 1991-92 growing seasons (Sass et al., 1994) and from ten different cultivars in 1993 growing season (Willis, 1995; Sass and Fisher, 1995) were cited to quantify the relationships of methane emission with soil, rice cultivar and grain yield. Under the similar soil sand content and agronomic management regime, total seasonal methane emission was positively correlated with rice grain yield and aboveground biomass at harvest. Linear relationships of daily methane emission with aboveground vegetative biomass and root biomass were also observed. On a carbon to carbon basis, the ratio of methane emission to rice net primary productivity was dependent on soil and rice variety, and increased with rice plant development. Models emphasized the contributions of rice plants to the processes of methane production, oxidation and emission and also the influence of environmental factors were developed to predict methane emission from flooded rice fields. Relative effects of soil texture, soil temperature and rice variety on methane production/emission were quantified by three dimensionless indices: soil index, temperature index and variety index, respectively. Model validation against observations from various regions of the world, including Italy, China, Indonesia, Philippines and USA demonstrated that methane emission can be predicted from rice growth and development, cultivar character, soil texture and temperature, and organic matter amendments. Of these, rice growth and development is a principal parameter governing the processes of methane production, oxidation and emission in irrigated rice paddies. Model estimates suggest that annual amount of methane emitted from Chinese rice fields ranges from 7.03 to 13.32 Tg CH$\sb4$ yr$\sp{-1}$ with an average value of 9.45 Tg CH$\sb4$ yr$\sp{-1}$ under permanent irrigation and the majority of methane was emitted in the region located at latitude between 25$\sp\circ$ and 32$\sp\circ$ N. Comparisons of estimated with the observed emissions show that the estimates were in general close to the measurements at most locations.
Polymers containing metal ions complexed by nitrogen-containing ligands
(1979) Bell, David Allen; Armeniades, C. D.; Leland, Thomas W.; Sass, Ronald L.
The feasibility of synthesizing the coordination compound [equation] and using it, as well as the complex [equation] to create polymer systems incorporating these complexes was investigated. These metal-organic complexes were used in epoxy-amine and formaldehyde-amine type polymerizations. The[equation] complex was synthesized according to Maerker's (1957) technique. This produced an impure product that could not be purified by recrystallization. Attempts to synthesize a pure complex by isolating the ligand and then reforming the complex failed because the instability of the complex in weak acids prevented the coordination reaction from occurring in suitable solvents, since the metal salts formed weak acids when dissolved. An unsuccessful attempt was made to synthesize a polymer from the impure[equation] complex and formaldehyde using techniques similar to those employed in the commercial manufacture of amine formaldehyde polymers. An epoxy crosslinking reaction was not attempted because no solvent could be found that would be compatible with both the complex and the epoxy resin. A molding powder synthesized from [equation] and formaldehyde failed to produce a polymer during compression molding because the complex decomposed on heating. An epoxy crosslinking reaction was not attempted. A polymer was synthesized from formaldehyde and 4,4' methylenedianiline using techniques similar to those commercially used in amineformaldehyde polymer manufacture. The polymer was brittle and inhomogeneous. A commercially available instrument used to measure the dynamic mechanical properties of polymers, the Rheovibron manufactured by the Toyo Measuring Instruments Co., was modified. These modifications extended the low temperature measurement limit from slightly below °C to liquid nitrogen temperatures. This instrument was then used to measure the dynamic mechanical properties of the 4,4' methylenedianilineformaldehyde polymer mentioned above and a polymer synthesized from 4,4' methylenedianiline and Epon 828, an epoxy resin made by the Shell Chemical Co. Measurements were taken over a temperature range of -17°C to +4°C.
Reducing Nitrogen Fertilizer Use to Mitigate Negative Environmental Impact in China
(2010) Huang, Yao; Sass, Ronald L.; Sun, Wenjuan; Zhang, Wen; Yu, Yongqiang; James A. Baker III Institute for Public Policy
Soil acetate and methane emissions from irrigated rice: The effects of field drainage and cultivar choice
(1996) Sigren, Lief Karl; Sass, Ronald L.
Methane emissions from flooded rice paddies are important contributors to the increasing atmospheric concentrations of methane, a potent greenhouse gas. With an increased need for rice agriculture to feed the growing global population, there is a need to develop methods that reduce methane emissions from rice paddies without adversely affecting grain yield. Two potential mitigation strategies were examined in this study: water management and cultivar choice. Previous studies indicate that floodwater management is a promising mitigation tool, with mid-season field drainage significantly reducing methane emissions. A variety of soil parameters, methane emissions, and soil porewater acetate concentrations were measured in outdoor pot and field water management studies. Acetate received particular consideration as it is a major precursor of methane formation within anaerobic soils. Field drainage caused rapid oxidation of the soil, with a sharp reduction in soil acetate concentrations, methane production, and methane emission rates. Evidence of drainage induced substrate depletion is presented as a possible mechanism responsible for the reduced methane production and emission after field drainage. Intervarietal differences in methane emission rates from rice have also been reported in previous studies. Methane emission rates and soil acetate concentrations were compared for a high emitting and a low emitting cultivar of rice. Significantly more soil acetate was present in the high emitting cultivar than the low emitting cultivar during the vegetative stage of plant growth. These results suggest that differences in methane emission between varieties of rice are the result of different methane production rates, not differences in methane transport processes. The different production rates are the result of differences in root carbon loss between the two cultivars. Neither of these strategies had an adverse effect on grain yield. The results strongly support the use of floodwater management and cultivar choice as methods to mitigate methane emissions from rice paddies.
The future of longleaf pine in a mixed pine-oak forest (Big Thicket, Texas)
(1996) Kaiser, Linda Carol; Sass, Ronald L.
A mixed pine-oak stand in the Turkey Creek Unit of the Big Thicket National Preserve was logged in 1929-1930 and has experienced no fires since at least 1974. Stand basal area, density, and species richness increased from 1980-1993. A stage projection of the longleaf pine population at the site indicates the population will slowly decline ($\lambda$ = 0.9957) after an initial increase in population size as the population approaches stable size class distribution. Survivorship in the largest size class, 50+ cm dbh, had the largest effect on the outcome. Variations on the base model with potential stronger negative effects from fire suppression reduced $\lambda$ only slightly. Alternatively, small changes in demographic characteristics reflecting positive effects of fire raised $\lambda$ above 1.00. The modeling results suggest that the population is resilient to long-term unfavorable conditions because of the longevity of individual trees.
The use of redox measurements to study methane mitigation options in Texas rice paddies
(1996) Lewis, Sandra Tracey; Sass, Ronald L.
Redox measurements were used to study whether different mitigation options affect methane emission and production by altering the electrochemical environment in rice paddy soil. These mitigation options include field drainage, use of different cultivars, and changing soil texture. Results indicate that the redox potential (Eh) is an accurate indicator of whether or not methane is produced. Also, the timing of methane production and emission was found to be dependent upon the reduction of iron and subsequent increase of the ferrous ion concentration. Field drainage is a mitigation option that successfully lowers methane emission rates by increasing the Eh. By studying the other mitigation options, it was found that once sufficiently negative Eh values are reached, different non-redox parameters control the actual amount of methane emitted.

Browsing by Author "Sass, Ronald L."

Results Per Page

Sort Options