Drinking water supplies contaminated with arsenic (As), a toxin and carcinogen, adversely impact the health of millions of people worldwide. Previous work has documented that different inorganic and organic As species vary with respect to their toxicities. It is, however, currently not well understood how As speciation affects bioavailability, defined as the capacity of a contaminant to cross an organism's cellular membrane, or how arsenic's form (dissolved vs. non-dissolved) can affect bioavailability. This dissertation addresses the effect of speciation and form on As bioavailability through a combination of field and laboratory studies. In the first project, a poultry litter application experiment was conducted to determine if trace elements (As, Cu, and Zn) are released from litter to underlying soil water, and if so, whether the trace elements are present in dissolved form or complexed to nanoparticles, colloids, or particles. Results showed that Cu and Zn released from the litter were dominantly complexed to organic matter or to iron oxides/clay particles, while As was dominantly dissolved or complexed to organic matter. In the second project, a luminescent E. coli bioreporter was created and exposed to different As species, including As(III), As(V), MSMA, and roxarsone. Results showed variable response, with As(III) producing the strongest response, followed by As(V) and MSMA; roxarsone showed no response. The bioreporter was exposed to As solutions with varying cation concentrations to examine the impact of sample geochemistry on performance. Increased monovalent (Na,K) concentrations enhanced luminescent response, while increased divalent (Ca) concentrations inhibited response. These altered responses reflect different As uptake pathways into the cell. The third study addressed bioavailability of As species to Corbicula fluminea, a clam commonly used for biomonitoring. Results demonstrate that As(III) is most bioavailable to Corbicula, followed by As(V), MSMA, and roxarsone. Corbicula also displayed the ability to change As speciation through internal processing and via their shell, demonstrating that Corbicula can affect As speciation in solution. Results of these studies enhance the scientific knowledge of how speciation and form affect As bioavailability, and can also inform regulators who use bioavailability to set remediation goals for As-contaminated systems. / Ph. D.

Aqueous silica is present in all natural waters and exhibits a high affinity for the surfaces of iron oxides. Therefore, it is expected to play an important role in environmental systems. Experiments were conducted to investigate the fundamentals of silica sorption onto pre-formed ferric hydroxide at pH 5.0-9.5 and silica concentrations of 0-200 mg/L as SiO₂. Over the entire pH range studied, sorption densities exceeding monolayer sorption were observed at silica levels typical of natural waters. Under some circumstances, sorption exceeded a monolayer while the particle zeta potential remained positive, a phenomenon which is inconsistent with available models. To address this deficiency, an extended surface complexation model was formulated in which soluble dimeric silica sorbs directly to iron surface sites. This model fits sorption density data up to 0.40 mol SiO₂/mol Fe, and it accurately predicts trends in zeta potential and the observed H⁺ release during silica sorption to ferric hydroxide at pH 5.0 and 6.0. A second phase of research was aimed at identifying the practical implications of silica sorption to iron hydroxide in natural and engineered systems. Two types of surfaces were prepared by exposing pre-formed Fe(OH)₃ to aqueous silica (0-200 mg/L as SiO₂) for periods of 1.5 hours or 50 days. The concentration of pre-formed iron passing through a 0.45 micron pore size filter at pH 6.0-9.5 increased as the solids aged in the presence of silica. Consistent with formation of small, stable colloids, "soluble" iron concentrations exceeded 0.2 mg/L only at zeta potentials <span style="text-decoration:underline"><</span> -15 mV. When arsenate was added to iron hydroxide particles equilibrated with silica for 1.5 hours, percentage arsenate removals were high. In contrast, arsenate removals decreased markedly as pH and silica concentrations increased if silica was pre-equilibrated with the iron for 50 days. Trends in percentage removal of humic substances were similar. Competition for sorption sites was the main cause of hindered anionic contaminant removal. However, interference with hydrolysis and precipitation are expected to be important under some circumstances, particularly during water treatment. / Master of Science

京都大学 / 新制・課程博士 / 博士(農学) / 甲第25320号 / 農博第2586号 / 新制||農||1104(附属図書館) / 学位論文||R6||N5492 / DGAM / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 髙野 俊幸, 教授 上髙原 浩, 教授 和田 昌久 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

This thesis presents an investigation into the factors affecting the morphology of hybrid inorganic/organic photoactive layers used in photovoltaic cells. Although optimisation of the organic (polymer) phase has received substantial attention, research into the morphology of the inorganic phase (semiconducting nanocrystals) remains limited. It is believed that there is a strong link between the morphology of the final photoactive film and the quality of the initial nanocrystal dispersion. To this end, two nanocrystal systems were investigated; zinc oxide (ZnO) and lead sulphide (PbS). ZnO nanocrystals were synthesised and found to possess reproducible characteristics. It was determined that colloid stability was initially dependent upon the presence of acetate groups bound to the surface, which in turn required a small quantity of methanol to be present in the organic dispersant. It was also discovered that while methanol evaporated readily from the surface of the nanocrystals, another molecule, 1-propylamine (1-PA), did not. Further investigations showed that while methanol only weakly physisorbed to the surface of ZnO nanocrystals, 1-PA formed strong, dative covalent bonds with Zn2+, preventing evaporation despite a low boiling point. Subsequent investigations into the effects of different ligands upon colloid stability found that amine-based groups typically possessed superior stabilising capabilities compared to alcohol-based analogues. The characteristics of nanocrystal / polymer blends were also investigated. It was determined that the nanocrystal dispersion became unstable at higher concentrations of polymer due to depletion aggregation. Films of nanocrystal / polymer blends were cast from dispersions containing either alcohol or amine-based ligands, and it was observed that dispersions stabilised with 1-PA possessed smooth morphologies on the micrometer scale. Investigations at the nanometer scale, however, revealed aggregates large enough to favour recombination.The latter half of this thesis regards the characterisation of PbS nanocrystals and investigations into triggered aggregation. It was determined that while PbS nanocrystals possessed reproducible characteristics, the stabilising molecule, oleic acid (OA) was insulating. The effects of exchanging the OA groups for a shorter ligand, butylamine (BA) were investigated.Finally, PbS nanocrystals were treated with a bidentate ligand, 1,2-ethanedithiol (EDT) to induce triggered aggregation. It was observed that the system was highly sensitive to the concentration of EDT in dispersion, forming small, relatively dispersed aggregates at low [EDT], and micrometer-sized crystalline structures at high [EDT]. The characterisation and entrapment of these nanocrystal structures within semi-conducting polymer films is also discussed.

This understanding of nanocellulose can be directly applied in future formulation design to use nanocellulose in polymer nanocomposites, foams, emulsions, latexes, gels and biomedical materials. / In this study, the potential of nanocellulose as a reinforcing agent in composite materials was investigated using atomic force microscopy (AFM). AFM was used to probe the mechanical properties of nanocelluloses and to investigate their interactions and adhesion in liquid media. Amplitude modulated-frequency modulated AFM was used to map the mechanical properties of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). Results showed Young’s moduli of 90 GPa and 120 GPa for CNCs and CNFs, respectively, which are comparable to literature values determined using other methods. Additionally, colloid probe AFM was implemented to observe the interactions (attractive, repulsive, steric, adhesive) between cellulose and silica colloid probes with anionic CNCs (containing either a Na+ or H+ counterion) and cationic CNCs. Colloid probe AFM measurements were carried out in five different liquid media: two salt solutions (NaCl and CaCl2) and three surfactant solutions (cationic cetyltrimethylammonium bromide, CTAB; anionic sodium dodecyl sulfate, SDS; and nonionic Triton X100). It was found that low salt concentrations resulted in electrostatic repulsion and high adhesion, whereas the reverse was observed at high salt concentrations. On the contrary, an increased surfactant concentration and increased number of surfactant aggregates (micelles, bilayers, etc.) resulted in increased adhesion. Surprisingly, the interactions were strongly dependent on the CNC counterion as surfactant adsorption seemed to be primarily driven by electrostatic interactions; CTAB adsorbed more to anionic CNCs, SDS adsorbed more to cationic CNCs and Triton X100 adsorbed minimally to all CNCs. Electrophoretic mobility and particle size data showed complementary results to colloid probe AFM, indicating that interactions between surfactants and CNC films and CNCs in suspension are closely related. This research suggests that CNCs have potential as reinforcing agents due to their high strength and the tunability of their interactions through the simple addition of salts or surfactants. This understanding can be directly applied in future formulation design to use nanocellulose in polymer nanocomposites, foams, emulsions, latexes, gels and biomedical materials. / Thesis / Master of Applied Science (MASc) / Nanocellulose is a sustainable nanomaterial most commonly extracted from plants and trees. In recent research, nanocellulose has been shown to have potential as a reinforcing agent for materials such as plastics, foams, paints and adhesives. In this study, the potential of nanocellulose was investigated using atomic force microscopy (AFM). As predicted, AFM measurements indicated that nanocellulose has a high stiffness, supporting the substitution of this biobased material in the place of metals and synthetic fibres. AFM was also used to examine particle interactions in salt and soap-like (surfactant) solutions; changes in nanocellulose size and charge were used to support the findings. Negatively charged nanocellulose interacted more with positively charged surfactants and vice versa. Low salt and high surfactant concentrations led to high adhesion and better material compatibility, which is preferred. This understanding can help us design better nanocellulose materials for future applications.

Oligonucleotides are popular recognition-based biomaterials assembly and disassembly tools due to their specificity and ease of control. Their susceptibility to degradation by nucleases and false positive signals under certain conditions, however, has led to great interest in chemically modified oligonucleotides such as locked nucleic acids (LNA) that enhance both nuclease resistance and target specificity. This dissertation extends prior work with DNA sequences to investigate incorporating locked nucleic acid (LNA), a synthetic oligonucleotide, in isothermal colloidal assembly and disassembly schemes as well as on hybridization kinetics between single-stranded and double-stranded probes immobilized on microspheres. Incorporation of LNA nucleotides into DNA sequences is of particular interest as a means of enhancing the performance of DNA in a biomaterials context due to the increased resistance of LNA to nuclease degradation, its greater intrinsic affinity for oligonucleotide targets, and low cytotoxicity effects. The effects of LNA modification, target sequence length, sequence fidelity, and salt concentration are key variables explored. After providing an overview of DNA and its properties, synthetic oligonucleotides, colloidal particles, and previous applications of DNA and LNA in colloidal assembly schemes, this work then discusses the selection and characteristics of appropriate pairs of hybridization partners for reversible colloidal assembly scenarios. A comparative investigation of the in situ primary hybridization kinetics between select LNA or DNA targets and single-stranded probes immobilized on colloidal surfaces is performed. To support the disassembly studies, the in situ competitive displacement kinetics of hybridized LNA primary targets by either LNA or DNA secondary targets is discussed. For these in situ studies, flow cytometry was used to quantify the hybridization reactions as they occur on microsphere surfaces. While comparable rate constants were typically observed between target and single-stranded probes, LNA typically exhibited more extensive primary and secondary hybridization activity. Optimizing hybridization parameters, such as duplex concentration, sequence fidelity, and LNA content in the probe and target strands, allows for the extent of colloidal disassembly to be tuned, an important step in developing a multifunctional colloid-based biomaterial system.

Many countries intend to achieve the safe management of their radioactive wastes through geological disposal. In addition, radioactively contaminated land is of global concern. To address both of these technical challenges it is imperative to understand the behaviour and subsequent migration of radionuclides in the subsurface. This thesis addresses uncertainties in the behaviour of the long-lived, risk-driving radionuclides U and Np in their most mobile and environmentally relevant oxidation states, U(VI) and Np(V). The formation the U(VI) colloidal nanoparticles is identified under the high pH, low carbonate conditions expected within the near field of a cementitious Geological Disposal Facility (GDF). XAS, SAXS, and TEM have been used to characterise these U(VI) colloids as 60-80 nm clusters of 1-2 nm clarkeite-like (Na uranate) nanoparticles, which are stable in cement leachate for a period of at least 5 years. The reactivity of these U(VI) colloids towards a range of mineral phases was investigated. In the presence of the common rock-forming minerals biotite, orthoclase, and quartz, only limited reactivity was observed with > 80 % of the U(VI) remaining in the filtered fraction after up to 5 years of reaction. In contact with cement, > 97 % of the U(VI) was removed from solution within 1 month. Reversibility studies, luminescence spectroscopy, and XAS suggest that a large portion of the cement associated U(VI) is in a uranophane-like coordination environment, likely incorporated into the C-S-H interlayers or as a stable surface precipitate. Together, this suggests that while U(VI) colloids could form in high pH (> 13) cement leachate, providing an additional pathway for migration, many of them are likely to be removed from suspension by the presence of solid cement, although 2.4 % (1.0 IμM) U(VI) remained in the filtered fraction even after 21 months of reaction. The interaction of aqueous U(VI) and Np(V) with a range of environmentally relevant Mn minerals has also been studied under circumneutral to alkaline conditions. Here, extensive (up to 99 %) uptake of U(VI) and Np(V) was observed in systems containing δ-Mn(IV)O2, triclinic (Na)-birnessite [Na0.5Mn(IV/III)2O4 · 1.5H2O], hausmannite [Mn(III/II)3O4], and rhodochrosite [Mn(II)CO3]. The uptake of U(VI) by δ-MnO2 and hausmannite was found to be partially irreversible, suggesting that these minerals could be particularly important in determining radionuclide migration. XAS indicated that both U(VI) and Np(V) formed edge-sharing bidentate adsorption complexes on the surface of δ-MnO2 and hausmannite, implying that these complexes are responsible for the observed reversibility. These complexes were also identified on triclinic (Na)-birnessite; however, after 1 month of reaction U(VI) was found to have migrated into the triclinic (Na)-birnessite interlayer, replacing Na+. Reaction with all three investigated Mn oxide phases was rapid, with equilibrium being reached within at least 2 weeks. However, whilst U(VI) and Np(V) were both extensively removed from solution in systems containing rhodochrosite, these reactions were much slower, with equilibrium taking up to 4 months to be established. XAS suggested that this was due to the formation of a U(VI) or Np(V) containing precipitate on the rhodochrosite surface.

This project focused on the study of self-assembling systems that can be inuenced by an external magnetic field, following the PhD research of Hauke Carstensen. My role was to study the behavior of beads and to optimize the tunable parameters so that the main force driving the dynamics of the system is the magnetic dipolar interaction between beads. To make sure that no other force plays an important role, we checked a number of things, the most problematic of which is flocculation in the colloid, which may happen if some beads get stuck to each other; to prevent them from aggregating we have to make sure that they have a large zeta potential, which will result in an electrically repulsive force between beads and will thus increase the stability of the colloid. We also have to make sure that other forces in the sample do not exceed the magnitude of magnetic forces between particles; examples of such forces can be the drag experienced while moving in the viscous ferrofluid, the gravity force or the random thermal movement of the molecules in the fluid. In order to study these efects, I measured the zeta potential of the magnetic and non-magnetic beads and later I added a surfactant compound (SDS) to our sample in order to increase said potential.

The number of poorly water-soluble drug substances in the pharmaceutical pipeline is increasing, and thereby also the need to design effective drug delivery systems providing high bioavailability. One favourable formulation approach is preparation of solid dispersions, where dispersing a poorly water-soluble drug in a water-soluble polymer matrix improves the dissolution behaviour and the bioavailability of the drug. However, in order to take full advantage of such formulations the impact of material properties on their performance needs to be investigated.   An experimental toolbox has been designed, and applied, for analysing the processes which govern the behaviour of solid pharmaceutical formulations in general, and that of solid dispersions in particular. For the purpose of monitoring multifaceted phenomena in situ during tablet dissolution, nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are superior to many other techniques, both on macroscopic and molecular levels. The versatility of NMR with its isotope and chemical selectivity allows one to follow the influence of the original tablet properties on polymer mobilisation, drug migration and water penetration selectively. Mapping these processes on relevant time scales in dissolving tablets highlighted the gel layer inhomogeneity below the originally dry tablet surface as a key factor for drug release kinetics.   Furthermore, NMR relaxometry has been shown to provide novel information about the particle size of the drug and its recrystallisation behaviour within swelling solid dispersions. The NMR experiments have been complemented and supported by investigation of the crystalline state, the powder morphology and the surface composition of the dry solid dispersions. These experiments have been performed by X-ray photoelectron spectroscopy (XPS),  scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic contact angle (DAT) measurements.   The methods presented in this thesis provide a new avenue towards better understanding of the behaviour of solid dispersions, which in turn may result in more effective distribution of promising drug candidates despite their low water-solubility. / En allt större andel av de läkemedelssubstanser som idag är av intresse för den farmaceutiska industrin är svårlösliga i vatten. För att trots detta erhålla hög biotillgänglighet måste man utveckla beredningsformer som medger effektiv frisättning av den aktiva substansen. En lovande sådan beredningsform utgörs av fasta dispersioner, där den svårlösliga substansen finfördelas i en vattenlöslig polymer. För att utnyttja dessa dispersioners potential fullt ut måste dock materialegenskapernas inverkan på deras beteende kartläggas i större utsträckning än vad som tidigare gjorts.   En uppsättning experimentella metoder har i detta arbete utvecklats och använts för att analysera de processer som styr beteendet hos fasta läkemedelsberedningar i allmänhet, och fasta dispersioner i synnerhet. För observation av sådana processer in situ, under pågående tablettupplösning, är NMR-spektroskopi (kärnmagnetisk resonans-spektroskopi) och NMR-avbildning överlägsna många andra tekniker, både på makroskopisk och på molekylär nivå. NMR är en mångsidig metod med både isotop- och kemisk selektivitet. Genom att utnyttja dessa möjligheter kan de enskilda sambanden mellan den ursprungliga tablettens materialegenskaper och polymermobilisering, vatteninträngning och den aktiva substansens migrering följas separat. Kartläggning av dessa processer, på relevanta tidsskalor i tabletter under upplösning, påvisar att gellagrets inhomogenitet inuti den ursprungliga tabletten har stor betydelse för frisättningskinetiken.   Vidare visar sig NMR-relaxometri ge värdefull information om den aktiva substansens partikelstorlek och dess omkristallisationsbeteende i fasta dispersioner under svällning och upplösning. NMR-experimenten kompletteras med oberoende karakterisering av det kristallina tillståndet, pulvermorfologin och ytsammansättningen hos de torra fasta dispersionerna. Dessa experiment utförs med hjälp av XPS (röntgen-fotoelektronspektroskopi), SEM (elektronmikroskopi), pXRD (pulver-röntgendiffraktion), DCS (differentiell kalorimetri), FTIR (infraröd Fourier transform spektroskopi) och DAT (dynamisk kontaktvinkel) mätningar.   De metoder som presenteras i den här avhandlingen pekar mot nya vägar att nå djupare förståelse för beteendet hos fasta dispersioner, vilket i sin tur kan leda till att fler lovande läkemedelssubstanser kan distribueras effektivt trots begränsad vattenlöslighet. / QC 20100915

Basic oxygen furnace (BOF) slag media were studied through a series of laboratory, modeling and field studies as a potential treatment material for use in on site wastewater disposal systems. Microsphere enumeration methodology was examined in a factorial experiment to evaluate the minimum density and minimum number of microspheres that should be counted to ensure accurate and precise estimations of concentration. The results suggest that to minimize variability at least 350 microspheres should be counted and a microsphere density of 25-40 microspheres field-1 is necessary. A review of existing methodologies for high-titer bacteriophage production was conducted and an amalgamation of existing methodologies was chosen that reliably achieves elevated concentration and ensures a purified suspension. A combination of batch and column studies was conducted to evaluate the removal of the bacteriophage, PRD-1, and virus-sized fluorescent microspheres by BOF media, and to delineate the relative contributions of the two principle attenuation processes, inactivation and attachment. In the batch studies, substantial removal of PRD-1 does not occur in the pH 7.6 and 9.5 suspensions, but at pH 11.4, removal of the virus was 2.1 log C/C0 day-1 for the first two days, followed by 0.124 log C/C0 day-1 over the subsequent 10 days. Two column studies were conducted after 60 and 300 days of saturation with artificial groundwater at a flow rate of 1 pore volume day-1 using two BOF mixtures. After 300 days of column saturation, microsphere concentrations approached input levels, indicating a removal of 0.1-0.2 log C/C0 and suggesting attachment processes were negligible. PRD-1 removal was more pronounced (1.0-1.5 log C/C0). The reduction of PRD-1 is likely the result of a combination of virus inactivation at elevated pH (10.6-11.4), and attachment processes. Geochemical factors controlling microsphere attachment were compared between the two sets of experiments after 60 and 300 days of column saturation. Differences in attachment efficiency may be due to higher influent DOC concentration in the second experiment, conversion of amorphous iron phases to more crystalline forms over time, reductive dissolution of preferable attachment sites on iron phases, or precipitation of calcite. Hydrus-1D, a one-dimensional numerical model, was used to quantify transport processes, inactivation and attachment/detachment, occurring in the column experiments by model inversion. Fitted microsphere breakthrough closely matched observed data, whereas PRD-1 breakthrough with realistic parameter values does not closely match the peaked nature of the observed curves. The model achieved improved fits for microsphere and PRD-1 breakthrough when both strongly- and weakly-binding sites are represented. A unique set of parameter estimates could not be determined because of overparameterization of the inverse modeling for the experimental systems. An alternative latrine incorporating BOF slag media was constructed in a periurban community located near São Paulo, Brazil. Pathogen indicator removal is approximately 4-5 orders of magnitude in less than one meter of vertical transport through the BOF slag media. In a control latrine, constructed with similar hydraulic characteristics and inert materials, comparable reductions in pathogenic indicators were observed over three meters of vertical transport.