Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 160-166).

Diss. (sammanfattning) Linköping : Univ. / Härtill 5 uppsatser.

Substances that consist of nano-scale fillers dispersed in a polymer matrix are known as polymer-nanocomposites (PNCs). These materials are appealing since they have high potentials for applications, due to their mechanical, electrical, and thermo electrical properties. A common problem associated with PNCs is that the nano-fillers have a tendency to aggregate into clusters and form phase separated domains, which cause the desired properties of the system to either diminish or vanish all together. Hairy nanoparticles (HNPs) can avoid the issue of agglomeration that is commonly encountered by conventional PNCs. When polymer chains are grafted to a nanoparticle, and the coverage is high, the nanoparticles have decreased inter-particle interactions which allows for enhanced dispersion and mixing into a polymer matrix. By tailoring the architecture (functionalization of polymer chains, degree of polymerization, grafting density) of HNPs, it is possible to control the final properties of the system. An in depth study was carried out to investigate the effects of hairy-nanoparticle architecture on the resulting properties of the material itself. Atom transfer radical polymerization and living anionic polymerization were used to synthesize the polymer chains, of the HNP systems, while various instrumental methods including differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) were utilized to study the physical ageing affects and self-assembly of these systems. #88ABW-2015-4971

This dissertation presents the synthesis and studies of polymer brush-supported organocatalysts and asymmetric mixed homopolymer brushes grafted on particles. The brushes were synthesized from initiator-functionalized particles by surface-initiated “living” radical polymerizations. Polymer brush-supported organocatalysts were designed to combine the advantages of both soluble polymer- (high activity) and crosslinked insoluble polymer-supported catalysts (recyclability). Chapter 1 describes the synthesis of a polymer brush-supported 4-N,N-dialkylaminopyridine (DAAP) catalyst from initiator-functionalized latex particles by surface-initiated nitroxide-mediated radical polymerization (NMRP). The hairy particles efficiently catalyzed the acylation of secondary alcohols and Baylis-Hillman reaction and were recycled  six times with no or negligible decrease in the reaction yield. Chapter 2 presents the synthesis of a thermosensitive polymer brush-supported DAAP by surface-initiated atom transfer radical polymerization (ATRP) from silica particles with addition of a free initiator. Both hairy particles and the free copolymer formed from the free initiator were used as catalysts for hydrolysis of nitrophenyl acetate at various temperatures. Below the lower critical solution temperature (LCST), the activity of hairy particles was very close to that of the free copolymer. LCST transitions exerted different effects on the reactions catalyzed by hairy particles and the free copolymer. Chapters 3 and 4 present the studies of the effects of chain length disparity and grafting density on phase morphology of mixed brushes grafted on silica particles. A series of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with a fixed PtBA molecular weight and various PS molecular weights were grown from silica particles functionalized with a monochlorosilane-terminated asymmetric difunctional initiator (Y-initiator) by sequential ATRP and NMRP. The total grafting densities of these brushes were 0.6 – 0.7 chains/nm2. The morphology of mixed brushes evolved from isolated PS nanodomains, to short PS cylinders, to a nearly bicontinuous nanostructure, and a two-layered nanostructure with the change of chain length disparity of two homopolymers. To study the grafting density effect, a set of high density asymmetric mixed brushes with total grafting densities of 0.9 – 1.2 chains/nm2 was prepared from triethoxysilane- terminated Y-initiator-functionalized silica particles. The feature sizes of the patterns formed from high density mixed brushes were much smaller than those of lower density mixed brushes.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1935. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 34-37).

Corn (Zea mays L.) and soybean (Glycine max L.) production in the Midwest US can result in significant nutrient leaching to groundwater and surface waters, which contributes to eutrophication and hypoxia in the Gulf of Mexico. A promising strategy to control nutrient leaching and sediment runoff loss during winter fallow period is the use of cover crops (CCs). In southern Illinois, CCs are not widely adopted by farmers due to economic constraints and the lack of scientific data that supports benefits of incorporating CCs into the corn-soybean rotation. Therefore, this doctoral dissertation addresses the critical question of the feasibility of the use of CCs in southern Illinois and is divided into three overarching research studies with different objectives divided into six research chapters. Research study 1 was a field experiment conducted from 2013 to 2017 to examine the effect of CCs (CC vs noCC) under two tillage systems [(no-tillage (NT) and conventional tillage (CT)] on aboveground plant attributes [dry matter yield, C:N ratio and nitrogen uptake (N uptake)], crop yields, available soil N content and N leaching in the vadose zone. The experimental layout was a randomized design with three rotations including corn-noCC-soybean-noCC [CncSnc], corn-cereal rye (Secale cereale L.) –soybean-hairy vetch (Vicia villosa R.) [CcrShv], and corn-cereal rye-soybean-oats+radish (Avena sativa L. + Raphanus sativus L.) [CcrSor] and two tillage systems. Soil samples collected after corn or soybean harvest and CC termination were analyzed for standard soil fertility parameters. Pan lysimeters installed below the ‘A’ horizon with depth varying from 22 to 30 cm were used for measuring soil solution nutrient concentration on weekly or biweekly basis depending on the precipitation. In NT system, the corn yield was 14% greater with CcrShv compared to CncSnc, whereas no significant difference existed in corn yield due to CC treatments within CT. Both CC treatments under NT reduced soybean yield by 24 to 27% compared to noCC. The rotations CcrShv and CcrSor with hairy vetch and oats+radish as preceding CCs resulted in 89% (37.73 vs 19.96 kg ha-1) and 68% (33.46 vs 19.96 kg ha-1) more nitrate-N (NO3-N) leaching than the CncSnc during cash crop season 2015. During the CC season in spring 2016, cereal rye CC in CcrShv and CcrSor reduced the NO3-N leaching by 84% (0.68 kg ha-1) and 78% (0.63 kg ha-1) compared to the CncSnc, respectively, under the CT system. Overall, our results indicated that the CT system had greater N leaching losses compared to NT system due to higher N availability in the tilled soil profile. The goal of the second research study was to understand the mechanisms of N cycling by CCs. Therefore, we applied 15N labeled urea fertilizer (9.2% atom) to corn that followed hairy vetch and noCC in May 2017 to evaluate the contribution of fertilizer and soil organic matter to N leaching and quantify the 15N content of surface runoff after storm events. During the 2017 corn season, repeated soil samples were collected and analyzed for 15N fertilizer recovery in soil at three depths. 15N recovery was higher in the corn that had hairy vetch as the preceding CC than the corn that had noCC by 13.13 and 3.68 kg ha-1 on soil sampling events of 7 and 21 days after planting of corn, respectively, at the depth 15-30 cm. Overall, the cumulative loss of 15NO3-N during corn season 2017 was <2% of the applied fertilizer. The contribution of NO3-N from soil organic matter to leaching was 61% higher for the corn rotation with hairy vetch CC compared to corn rotation with noCC (1.12 vs 0.69 kg ha-1). Research study 3 evaluated the effects of CCs (cereal rye and hairy vetch) and topography (shoulder, backslope, footslope) on corn-soybean production, soil and water quality, nutrient and sediment export in agricultural headwater streams in a paired-watershed experimental design. The crop rotation followed in the CC-watershed was corn-cereal rye-soybean-hairy vetch whereas the rotation in the noCC watershed was corn-noCC-soybean-noCC. Use of hairy vetch CC increased N uptake at shoulder, backslope and footslope positions by 110.90, 85.02, and 44.89 kg ha-1, respectively, when compared to noCC treatment. The corn yield at the shoulder position was increased by 69% in CC-watershed compared to noCC watershed in 2017 likely by providing large N additions following decomposition. Cereal rye increased soybean yield by 17% and 8% at the shoulder and backslope position, respectively in 2016. Additionally, the effects of topography and CCs on soil N levels and N leaching in the watersheds were also evaluated. The NO3-N concentrations measured using suction cup lysimeters in CC-watershed were reduced by 2.54 mg L-1 (67%) when compared to noCC watershed. During the hairy vetch CC season, the reduction in NO3-N concentrations in soil solution was only seen at the footslope position. The excessive N at footslope positions may have been immobilized or denitrified due to soil waterlogging from higher water availability at the footslope. Forty-two and 18 storm events were collected during a 4-yr calibration period and CC-treatment period, respectively. Predictive regression equations developed from the calibration period were used for calculating TSS, NO3-N, NH4-N, and DRP losses of surface runoff for the CC-treatment watershed. The CCs reduced TSS and discharge by 33% and 34%, respectively in the CC-watershed during the treatment period. However, EMCs for NO3-N, NH4-N, and DRP did not decrease. Overall, CCs are a recommended conservation practice for farmers who want to enhance the long term profitability of their production systems, while building soil health and protecting downstream water quality. The CCs have the potential to reduce nutrient leaching, peak/total discharge, improve soil quality and crop yields. However, reduction in leaching will depend on the type of CC (legume vs non-legume crops) used in rotation, the time of termination of CCs, cover crop establishment and number of years under CCs. Synchronizing N availability from CCs to N uptake by cash crop is important for reducing nitrate leaching and increasing crop yields.

Genomic diversity is shaped by the interplay between mutation, genetic drift, recombination, and natural selection. A major goal of evolutionary biology is to understand the relative contribution of these different microevolutionary forces to patterns of genetic variation both within and across species. The advent of massive parallel sequencing technologies opened new avenues to investigate the extent to which alternative evolutionary mechanisms impact the genome and the footprints they leave. We can leverage genomic information to, for example, trace back the demographic trajectory of populations and to identify genomic regions underlying adaptive traits. In this dissertation, I employ genomic data to explore the role of demography and natural selection in two New World bird systems distributed along steep environmental gradients: the Altamira Ori-ole (Icterus gularis), a Mesoamerican bird that exhibits large variation in body size across its range, and the Hairy and Downy woodpecker (Dryobates villosus and D. pubescens), two sympatric species whose phenotypes vary extensively in response to environments in North America. In Chapter 1, I combine ecological niche model, phenotypic and ddRAD sequencing data from several individuals of I. gularis to investigate which spatial processes best explain geographic variation in phenotypes and alleles: (i) isolation by distance, (ii) isolation by history or (iii) isolation by environment. I find that the pronounced genetic and phenotypic variation in I. gularis are only partially correlated and differ regarding spatial predictors. Whereas genomic variation is largely explained by historical barriers to gene flow (IBH), variation in body size can be best predicted by contemporary environmental heterogeneity (IBE), which is consistent with a pattern produced by either natural selection or environmental plasticity. In Chapter 2, I conduct whole genome resequencing on 140 individuals of Downy and Hairy Woodpecker from across North America to more explicitly elucidate the impact of demography and natural selection on the genome. I find that despite spatial congruence in allele frequencies, population structure in these two species has been produced at different temporal scales. Whereas Hairy Woodpeckers were isolated into two east-west glacial refugia, Downy woodpecker populations seem to have expanded from a single ancestral refugium. Demographic analyses suggest large variation in Ne over the past one million years in both Hairy and Downy Woodpeckers, with repeated episodes of bottleneck followed by population expansion, consistent with the onset of the climatic oscillations of the Pleistocene. Nucleotide diversity in both species was positively correlated with recombination rate and negatively correlated with gene density, suggesting the effect of linked selection. The magnitude of this effect, however, seems to have been modulated by the individual demographic trajectory of populations and species. Nevertheless, patterns of nucleotide diversity along the genome are highly correlated between Hairy and Downy Woodpecker, which may be attributed to pervasive selection acting on a conserved genomic landscape of recombination. Finally, in Chapter 3, I use a suite of statistical methods to scan the genome of Hairy and Downy Woodpecker for signatures of natural selection associated with population-specific environmental differences. I test whether climatic adaptation was achieved through selection on the same loci in both species, which would indicate parallel genetic mechanisms for adaptation. I find limited evidence of genomic parallelism at the SNP level, but large parallelism at the gene level. Candidate genes were involved in a broad range of biological processes, including immune response, nutritional metabolism, mitochondrial respiration, and embryonic development. Lastly, I identify potential candidates for key phenotypic traits in Downy and Hairy Woodpecker, such as genes in the IGF signaling pathway, putatively linked to differences in body size, and the melanoregulin gene (MREG), potentially involved in plumage variation. Together, these findings highlight the significant role of demography and natural selection in shaping genomic variation.

No description available.

The diverse cropping system of eastern Virginia's coastal plain offers limited opportunity to establish winter annual cover crops (WCC) for nitrogen (N) scavenging. The winter fallow niche after double-crop or full-season soybean (Glycine max L. Merr.) encompasses the majority of acres left fallow. Our objective was to evaluate interseeded WCC N scavenging performance following soybean and N supplying capacity to subsequent corn (Zea mays L.). Field studies were conducted at four different locations in each of the two study years. The experimental design was split plot with cereal rye, hairy vetch, and RV mix WCC as main plots and ten fertilizer nitrogen (FN) rates in a factorial arrangement (0 and 45 kg FN ha-1 as starter; and 0, 45, 90, 135, and 180 kg FN ha-1 at sidedress) to corn as subplots. The highest N uptake for cereal rye at winter dormancy was 18 kg N ha-1, but the average was 6-7 kg N ha-1. At WCC termination average N uptake for cereal rye was 35 and 40 kg N ha-1 in 2013 and 2014, respectively. Average biomass dry matter (DM) at WCC termination for cereal rye, cereal rye + hairy vetch mix (RV mix), and hairy vetch was 2356, 2000, and 1864 kg ha-1 in 2013; and 2055, 2701, and 692 kg ha-1 in 2014, respectively. Average cereal rye N uptake was 35 kg N ha-1 in 2013 and 40 kg N ha-1 in 2014. Significant differences for residual soil nitrogen were most apparent for soil nitrate (NO3-N) at lower depths (15-30 and 30-60 cm) during WCC termination and in the upper 0-15 cm during corn growth stage (GS) V4 of both years. Corn grain yield plateau following hairy vetch WCC was 0.7 and 0.6 Mg ha-1 higher than when following cereal rye WCC at zero and 45 kg ha-1 starter FN, respectively. Average agronomic optimum FN rates (AONR) were 26 and 9 kg ha-1 lower following hairy vetch than cereal rye WCC at zero and 45 kg ha-1 starter FN, respectively. Estimated hairy vetch FN reductions by FN replacement and AONR difference methods were 48 and 18 kg FN ha-1 in plots receiving zero starter FN; and 58 and -43 kg FN ha-1 in plots receiving 45 kg ha-1 starter FN. In-season soil N tests did not offer adequate information in order to predict sidedress FN reductions. These findings suggest that cereal rye and RV mix have the potential to scavenge and conserve residual soil N and hairy vetch is more than capable to supply PAN to subsequent corn when interseeded into soybean. / Master of Science

Die Pflanzenbiotechnologie ermöglicht die nachhaltige Gewinnung pflanzlicher Wertstoffe mittels innovativer biotechnologischer Methoden. Bisher mangelt es auf diesem Gebiet jedoch an Grundlagenwissen und aussagekräftigen Studien, z. B. zur Anwendung biotechnologischer Standardverfahren beim Respirationsmonitoring. Im Rahmen der vorliegenden Arbeit werden grundlegende Untersuchungen zur Erzeugung (Induktion) pflanzlicher in-vitro-Kulturen und zu geeigneten Kultivierungssystemen sowie Prozessüberwachungsstrategien vorgestellt und diskutiert. Als Modellsystem dient die Einjährige Sonnenblume Helianthus annuus. Die Induktion pflanzlicher Zellkulturen (Kallus und Suspensionen) mit photomixotrophem Stoffwechsel wurde unter unterschiedlichen Bedingungen untersucht und geeignete Induktionsparameter ermittelt. Sowohl pflanzliche Gewebekulturen (Hairy roots) als auch die erzeugten photomixotrophen und heterotrophe Suspensionen konnten in verschiedenen Reaktorsystemen erfolgreich kultiviert und die Produktbildung nachgewiesen werden. Protokolle zu Induktion sowie Erhaltung von Zell- und Gewebekulturen von H. annuus wurden etabliert. Ein modernes Prozessüberwachungssystem für Schüttelkolben, das RAMOS® (Respiration Activity Monitoring System®) wurde erstmals umfassend für Untersuchungen des Wachstumsverhaltens und zum Screening pflanzlicher Zell- und Gewebekulturen eingesetzt. Dabei wurde die Problematik der Verdunstung (Evaporation) aus den Kulturgefäßen als signifikant bei den langen Kultivierungen von pflanzlichen in-vitro-Kulturen diagnostiziert und ein Modell zur Korrektur der Atmungstransferraten entwickelt. Erstmalig in der Pflanzenbiotechnologie kam das RAMOS® für Studien mit Zell- und Gewebekulturen von H. annuus im Speziellen sowie für Untersuchungen von Hairy roots im Allgemeinen zum Einsatz. Mit Hilfe der vorliegenden Arbeit werden relevante Kriterien zur Anwendung des innovativen Messsystems RAMOS® im Rahmen pflanzenbiotechnologischer Untersuchungen vorgestellt. Es wird ein Überblick über geeignete Kultivierungssysteme und zu publizierten Modellierungsstrategien für Applikationen in der Pflanzenbiotechnologie gegeben. Ein Literaturüberblick zu publizierten Modellierungsstrategien mit pflanzenbiotechnologischem Bezug vervollständigt die Arbeit. / Plant biotechnology enables a sustainable production of valuable plant resources using innovative biotechnological methods. However, a comprehensive knowledge base as well as significant studies, e. g. concerning the application of biotechnological standard procedures of respiration monitoring, are missing so far. In this work, basic investigations regarding the induction of plant in vitro cultures and appropriate cultivation systems as well as process monitoring strategies will be introduced and discussed. The annual sunflower Helianthus annuus serves as biological model system. The induction of plant cell cultures (callus and suspension) with photomixotroph metabolism was investigated at different conditions and appropriate induction parameter were determined. Both, plant tissues (Hairy roots) and induced photomixotroph as well as heterotrophic suspensions were cultivated successfully in various reactor systems. The production of desired metabolites was proven. Protocols concerning induction respectively maintenance of cell and tissue cultures of H. annuus have been established. For extensive investigations of growth behavior and for screening of plant cell and tissue cultures, a modern process monitoring tool for shake flasks, the RAMOS® (Respiration Activity Monitoring System®), was used for the first time. Thereby, the problem of evaporation off the culture vessels was identified as significant for time-intensive cultivations of plant in vitro cultures. A model for the correction of respiration transfer rates has been developed. For the first time in plant biotechnology, the RAMOS® has been applied for studies with H. annuus in special, and for studying the growth and respiration behavior of Hairy roots in general. With the help of the present work, relevant criteria concerning the application of the innovative measuring system RAMOS® for plant biotechnological investigations will be given. Furthermore, a survey over appropriate cultivation systems and published modelling strategies in plant biotechnology are introduced. A literature survey concerning model strategies regarding plant biotechnology completes this work.