Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 129-136).

Η μεσόμορφη κατάσταση είναι μια ενδιάμεση κατάστασή της ύλης μεταξύ στερεής και υγρής φάσης και περιλαμβάνει δύο μεγάλες κατηγορίες, την υγροκρυσταλλική και την περιστροφική φάση, στις οποίες παρατηρούνται ιεραρχημένες δομές υπό συγκεκριμένες συνθήκες. Ανάλογη συμπεριφορά εμφανίζουν και τα ημιφθοριωμένα αλκάνια κατά το σχηματισμό κρυστάλλων σε στοιβάδες (λαμέλες) με μικρή ή μεγάλη τάξη στη μεσοφάση τους τα οποία έχουν μοριακό τύπο CmF2m+1CnH2n+1 και χρησιμοποιούνται κατά κόρον σε βιοϊατρικές εφαρμογές. Ένα από αυτά τα αλκάνια είναι το F(CF2)12(CH2)12H ή αλλιώς F12H12, ένα γραμμικό δισυσταδικό μόριο για το οποίο έχει παρατηρηθεί ότι μεταπίπτει από μία μεσοφάση με δομή διστρωματικής λαμέλας σε μεσοφάση μικρότερης τάξης και δομής μονομοριακής λαμέλας καθώς η θερμοκρασία αυξάνει. Στη παρούσα εργασία, με τον ανασχεδιασμό ενός ατομιστικού αλγορίθμου Monte Carlo (MC) μελετήθηκε η μεσόμορφη κατάσταση του F12H12 και συγκεκριμένα στόχος ήταν η πρόβλεψη της αυτό-οργάνωσης του συστήματος στον κύριο όγκο (bulk system) και στην ενδιάμεση κατάστασή του. Όμως για να καταστεί εφικτή αυτή η μελέτη, ήταν αναγκαία η εύρεση από την διεθνή βιβλιογραφία ενός μοριακού μοντέλου, το οποίο θα μπορούσε να προβλέψει με την καλύτερη δυνατή ακρίβεια τις ιδιότητές του υπό μελέτη συστήματος. Προς την κατεύθυνση αυτή, δοκιμάστηκαν τρία μοριακά μοντέλα με διαφορετικές παραμέτρους αλληλεπίδρασης των ατομιστικών μονάδων του μορίου. Τα αποτελέσματα των προσομοιώσεων Monte Carlo δεν ήταν τα αναμενόμενα, σύμφωνα με τα διαθέσιμα πειραματικά δεδομένα. Η ιδέα της εφαρμογή της μεθόδου μοριακής δυναμικής για τη μελέτη της μεσόμορφης κατάστασης των F12H12 κρίθηκε απαραίτητη για την εξισορρόπηση του συστήματος σε εύλογο χρονικό υπολογιστικό διάστημα, αλλά και για τη χρήση της ως εργαλείο ελέγχου της αξιοπιστίας του αλγορίθμου MC και των μοριακών μοντέλων. Από τα αποτελέσματα προσομοιώσεων MD εξακριβώθηκε η ορθότητα του αλγορίθμου MC και προέκυψε το συμπέρασμα ότι τα εξεταζόμενα μοριακά μοντέλα αδυνατούν να προβλέψουν με ακρίβεια και επιτυχία τα πειραματικά δεδομένα, καθώς τουλάχιστον τα δύο από αυτά εντοπίζουν τη μετάβαση φάσης από την ισοτροπική στην μεσόμορφη κατάσταση μικρότερης τάξης σε διαφορετικές συνθήκες (μικρότερη θερμοκρασία, μεγαλύτερη πυκνότητα) από αυτές των πειραματικά μετρούμενων. Σε αυτές τις συνθήκες εφαρμόστηκε και η μέθοδος προσομοίωσης Monte Carlo η οποία δεν είχε την δυνατότητα να εξισορροπήσει το υπό μελέτη σύστημα σε μικρές θερμοκρασίες και να προβλέψει την μετάβαση φάσης. Σε κάθε περίπτωση θα ήταν εξαιρετικά ενδιαφέρουσα η περαιτέρω μελέτη του συστήματος F12H12. / Semifluorinated alkanes (SFAs) are diblock molecules, which consist of two immiscible and incompatible moieties, the perfluorinated segment (CF2)m and the hydrοgenated segment (CH2)n, which are covalently linked to form the copolymer with the general chemical structure F(CF2)m(CH2)nH, abbreviated as FmHn. The (CF2)m and (CH2)n segments have different conformation, as the first one adopts a twisted 15/7 helical structure, whereas the other prefers an all-trans zigzag conformation. Due to the incompatibility between the two segments and consequently their asymmetric structure, SFAs are capable of remarkable phenomena, such as structural transitions, formation of ordered structure and aggregations in non-polar solvents, influenced by the existence of significant dipole moment and surface activity. In spite of the absence of hydrophilic polar head group from the diblock, SFAs possess an amphiphilic character and form Langmuir monolayers at the air/water interface. Furthermore, because of their biocompatibility and their tendency to stabilize interfacial films and control properties of biological colloidal systems, they have been used as additional components in fluorocarbon-in-water emulsion applicants to artificial blood formulation, in phospholipid liposomes that act as drug delivery systems, in ophthalmology as endotamponades, in vitreoretinal surgery and in lung surfactant therapy. Despite the amply of studies as far as the structure and the behavior of solid state SFAs, the identification of phase transition structure has not clearly spelled out, but for some FmHn it has eventually been described as liquid crystalline or smectic phase. Experimental efforts to predict the solid state packing structures in the bulk and the phase state of SFAs, arising from the incommensurable cross-section of the two opposing moieties, with comparable segment lengths and especially for F12Hn compounds have attracted the scientific interest in the literature. DSC measurements indicate the existence of solid-solid phase transitions for F12Hn with n= 8, 10 and 12. Two different crystal packings with layered structure have been observed below the melting point of F12Hn by SAXS and electron density profiles. It is proposed that F12Hn chains with 8 ≤ n ≤ 14 form an antiparallel monolayer packing below their melting point and at lower temperature it follows the transformation to a tilted bilayer lamella, as the Bragg spacings are larger than the end-to-end distance of the individual molecules. For the same group of F12Hn, their phase is referred as a mesomorphic phase below the melting transition and it is described as a “smectic liquid crystalline phase”, whereas at the solid-solid transition the hydrogenated segment presents a fluidlike character. Semifluorinated alkane F(CF2)m(CH2)n with m=n=12 is a linear, symmetric diblock, that is abbreviated as F12H12. It exhibits interesting morphologies not only in the air/water interface, as it forms Langmuir monolayers consisting of “spherical cap” substructures with the orientation of the perfluorocarbon segment on the air1, but also in the bulk state. The DCS experiments and the thermodynamic pressure-volume temperature measurements proposed that the F12H12 system undergoes solid-solid transitions and especially favors two first order transitions. Brillouin spectroscopy, X-ray scattering studies and NMR experiments showed that F121H12 below its melting point exhibits phases that are denoted as layered smectic phases or lamellar phases. In particular, below Tm ~361-363K (melting point) a mesophase exists, whose structure is composed from a monolayer lamella in which hydrocarbon and perfluorinated segments display interdigitation. At lower temperatures (Ts ~351-353K) the system exhibits a denser solid phase that comprises of a fluorocarbon bilayer lamella with interdigitated hydrocarbon segments. In this present work, we report results of constant pressure atomistic molecular simulations, both using molecular dynamics and Monte Carlo methods and adopting a molecular united model, for predicting the phase transition and the solid bulk-phase assembly of F12H12 molecules. Furthermore, thermodynamic and structural properties are studied and thus the evaluation of the predictions obtained from the two methods is sought through comparison with the available experimental data.

Analysis of cuticular wax from Kalanchoe daigremontiana leaves was performed to identify the constituent components within the wax, determine how these changed during leaf ontogenesis, and discover how they were distributed within the cuticle. Analysis of extracted cuticular wax by gas chromatography, mass spectrometry, and comparison with authentic standards led to the identification of triterpenoids including glutinol, friedelin, germanicol, epifriedelanol, glutinol acetate and β-amyrin as well as very long chain fatty acid (VLCFA) derivatives including alkanes, primary alcohols, aldehydes, fatty acids, and alkyl esters. Cuticular wax composition in young K. daigremontiana leaves was dominated by triterpenoids, which made up over 70% of the lipid soluble compounds. During leaf ontogenesis, wax composition changed to include a higher proportion of VLCFA derivatives, which made up approximately 50% of cuticular wax in mature leaves. The most abundant triterpenoids in the wax were glutinol and friedelin, both fairly uncommon pentacyclic triterpenoids with a complex proposed biosynthetic mechanism. Tritriacontane (C33 alkane) was the most abundant compound within the VLCFA derivatives. Cuticular wax accumulation was found to correspond well to leaf growth, with both processes slowing at the same time. Variations in the ratio of friedelin-like compounds to glutinol-like compounds during leaf ontogenesis suggest the presence more than one active triterpenoid synthase enzyme in the leaves of K. daigremontiana. VLCFA compounds were found mainly in the epicuticular wax on both the adaxial and abaxial surfaces, while triterpenoids were relatively more abundant in the intracuticular layer. Two different epicuticular wax crystal forms were observed by scanning electron microscopy (SEM) which can be described as platelets with sinuate margins and twisted ribbons. Based on SEM and chemical data as well as previous reports of crystal composition, it is hypothesized that each crystal type has a unique composition, with the platelets containing one or more triterpenoids and the twisted ribbons containing alkanes and other VLCFA derivatives. Confirmation of this hypothesis will have to await further investigation. This research provides information that will aid in the larger goals of characterizing a glutinol or friedelin synthase and understanding the gradients established within epicuticular and intracuticular wax layers.

Project I: [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 as a Homogeneous Hydrogenation Catalyst for Biomass Derived Substrates. The complex [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 has been shown to be an active ionic hydrogenation catalyst for selected carbonyls, diols and glycerol by the Schlaf group. It was postulated to also be active for other biomass derived substrates such as levulinic acid (LA), furfural and 5-hydroxymethyl furfural (HMF). Synthesis of the complex was optimized and full characterization carried out by 1H/13C –NMR. The complex was tested against LA in aqueous sulfolane medium and the furfural/HMF model system 2,5-hexanedione in water. Activity of the complex was compared to the analogous metal-ligand bifunctional (MLB) system described in Project II. The complex exhibited good thermal stability up to 200 oC in 90/10 wt% sulfolane/water mixtures and was capable of hydrogenation of LA to γ-valerolactone in 95% yield. Addition of protic acids to the reaction mixture and increasing proportions of water decreased the activity of the complex towards the hydrogenation of LA. Project II: [Ru(OH2)3(di(picolyl)amine)](OTf)2 as an acid-, water- stable, metal-ligand bifunctional deoxygenation catalyst. The complex [Ru(OH2)3(di(picolyl)amine)](OTf)2 was postulated to be an active MLB ionic hydrogenation catalyst under acidic aqueous conditions. Using the substantially labile [Ru(DMF)6](OTF)3 ruthenium complex as the precursor, the desired complex was prepared insitu by coordination of the DPA ligand and concomitant reduction of Ru3+ to Ru2+. The complex was characterized by 1H/13C-NMR and tested for the hydrogenation of LA, 2,5-hexanedione, furfural and HMF under acidic aqueous conditions. The complex exhibited thermal stability up to 150 oC and was active for the hydrogenation of carbonyls, as demonstrated by the conversion of 2,5-hexanedione to 2,5-hexanediol in 94% yield in water. Addition of H3PO4 as an acid cocatalyst resulted in nearly complete conversion to dimethyltetrahydrofuran (DMTHF) but further deoxygenation could not be achieved. Direct comparision of [Ru(OH2)3(di(picolyl)amine)](OTf)2 and [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 under identical conditions against LA and 2,5-hexanedione demonstrated that the[Ru(OH2)3(di(picolyl)amine)](OTf)2 catalyst is more active than the [Ru(OH2)3(4'-phenyl-2,2':6',2''-terpyridine)](OTf)2 complex in all cases, suggesting that the di(picolyl)amine complex operates through a MLB ionic hydrogenation mechanism. / NSERC

In April 2010, approximately 4.9 million barrels of oil were accidentally released into the Gulf of Mexico during the Deepwater Horizon Macondo Mc252 Oil Spill. Some of the surface oil was carried by prevailing winds and currents and reached the coast of Louisiana impacting marsh and marine ecosystems. One and a half years after this incident, a set of oiled marsh samples (2 grab samples) coupled with nearby subtidal and intertidal cores (12 cores) were collected from Barataria Bay, Louisiana to determine the probable source of petroleum residues present and to characterize the chemical composition of the oil. Plus, pre-spill core which was collected from Barataria Bay in 2007 was analyzed to identify the background hydrocarbon composition of the area. Polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), biomarker, and stable carbon isotope compositions of selected samples were detected using a GC-MS and an elemental analyzer Conflo system coupled to a DeltaPlusXP isotope ratio mass spectrometer. The comprehensive chemical data allowed us to classify the pre and post-spill samples into 4 Groups. According to this classification, Group 1 and Group 2 samples had the highest concentrations of petroleum-derived hydrocarbons. Group 3 and background samples, on the other hand, was dominated by biogenic signatures. Although a direct connection between the detected and spilled Macondo oils results are complicated due to confounding factors (e.g., already present hydrocarbons and weathering processes), our biomarker data indicates that both oils have similar signatures. This close genetic relationship was also identified by stable carbon isotope analysis. The impact of the Macondo Mc252 Oil Spill in Barataria Bay appears to be limited to areas closer to the source. The oil has undergone moderate weathering and has penetrated into, the at least, the top 9 cm sediments. Additionally, to examine the decadal-scale history of sedimentation in these marshes, a sediment core was analyzed for the radioisotope 137Cs. The observed sedimentation rate of 0.39 cm/yr shows that oil pollutant input into Barataria Bay has been ongoing for at least 50-60 years.

Chlorinated paraffins (CPs) are ubiquitous environmental contaminants. They fulfill all of the criteria (persistent, toxic, and subject to long-range transport) for persistent organic pollutants (POPs) according to the United Nations Economic Commission for Europe (UNECE). CPs are also under consideration for inclusion in the Stockholm Convention on POPs. Their presence has been shown in various environmental matrices in the industrialized parts of the world, as well as in remote regions such as the Arctic. The aim of this thesis was to increase the limited knowledge of the presence of CPs in the environment, their sources to the environment, and the resulting human exposure. An analytical procedure for the determination of CPs in environmental samples based on gas chromatography coupled to electron capture detection (GC-ECD) has been developed. GC-ECD is a relatively inexpensive instrument that is fast and easy to operate. These advantages open up the possibility for a comprehensive screening of the occurrence of CPs in the environment, including developing countries. Furthermore, the occurrence of CPs in ambient air and in indoor air and dust was studied. Elevated CP concentrations in indoor air (<5-210 ng/m3) were observed compared to ambient air (0.7-33 ng/m3), which is indicative of the presence of indoor emission sources. Indoor air and dust concentrations were used to estimate the human exposure to CPs via the indoor environment. Comparison of the estimates to available dietary intake estimates indicated that the indoor exposure pathways are not negligible. CP concentrations in ambient air from urban Stockholm were higher than in rural Aspvreten, Sweden. This indicates the presence of additional (emission) sources in urban areas compared to rural sites. Additionally, a seasonal variation of air concentrations was observed at both locations, suggesting temperature dependent emission sources for CPs. These observations were supported by a substance flow analysis of CPs performed for Stockholm. This study estimated the major emission sources of CPs to the Stockholm environment to be emissions from painted surfaces and in-place sealants. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

Analysis of cuticular wax from Kalanchoe daigremontiana leaves was performed to identify the constituent components within the wax, determine how these changed during leaf ontogenesis, and discover how they were distributed within the cuticle. Analysis of extracted cuticular wax by gas chromatography, mass spectrometry, and comparison with authentic standards led to the identification of triterpenoids including glutinol, friedelin, germanicol, epifriedelanol, glutinol acetate and β-amyrin as well as very long chain fatty acid (VLCFA) derivatives including alkanes, primary alcohols, aldehydes, fatty acids, and alkyl esters. Cuticular wax composition in young K. daigremontiana leaves was dominated by triterpenoids, which made up over 70% of the lipid soluble compounds. During leaf ontogenesis, wax composition changed to include a higher proportion of VLCFA derivatives, which made up approximately 50% of cuticular wax in mature leaves. The most abundant triterpenoids in the wax were glutinol and friedelin, both fairly uncommon pentacyclic triterpenoids with a complex proposed biosynthetic mechanism. Tritriacontane (C33 alkane) was the most abundant compound within the VLCFA derivatives. Cuticular wax accumulation was found to correspond well to leaf growth, with both processes slowing at the same time. Variations in the ratio of friedelin-like compounds to glutinol-like compounds during leaf ontogenesis suggest the presence more than one active triterpenoid synthase enzyme in the leaves of K. daigremontiana. VLCFA compounds were found mainly in the epicuticular wax on both the adaxial and abaxial surfaces, while triterpenoids were relatively more abundant in the intracuticular layer. Two different epicuticular wax crystal forms were observed by scanning electron microscopy (SEM) which can be described as platelets with sinuate margins and twisted ribbons. Based on SEM and chemical data as well as previous reports of crystal composition, it is hypothesized that each crystal type has a unique composition, with the platelets containing one or more triterpenoids and the twisted ribbons containing alkanes and other VLCFA derivatives. Confirmation of this hypothesis will have to await further investigation. This research provides information that will aid in the larger goals of characterizing a glutinol or friedelin synthase and understanding the gradients established within epicuticular and intracuticular wax layers.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 222-228). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2004. / Typescript. Vita. Includes bibliographical references (leaves 222-228). Also available on the Internet.

O trabalho foi conduzido na EEA-UFRGS, em Eldorado do Sul/RS, entre jan/2009 e fev/2010 com o objetivo de avaliar as relações entre comportamento ingestivo, consumo de forragem, oferta diária de forragem e as variáveis da estrutura do pasto a fim de definir ambientes adequados ao pastejo em pastagem natural complexa. Para avaliar o tempo diário das atividades de novilhas de corte, verificou-se o potencial de um método acústico, enquanto que para avaliar o consumo de matéria seca utilizou-se a técnica dos alcanos, a partir da teoria do duplo alcano. Foi utilizado um delineamento experimental de blocos completos casualizados com duas repetições. Os tratamentos consistiram dos seguintes níveis de oferta diária de forragem aplicados desde 1986: 4, 8, 12 e 16 kg de MS/100 kg de PV, ou % PV. Foram utilizadas novilhas mestiças com 15 meses de idade e 152±4,0 kg, alocadas na área em Nov/2008. As variáveis utilizadas para descrever a estrutura dos pastos foram: massa de forragem, altura do pasto e frequência de touceiras. As variáveis de comportamento ingestivo consideradas foram: tempo de pastejo, deslocamento e taxa de deslocamento diário em pastejo. Já as variáveis de consumo estudadas foram: consumo e taxa de consumo diário de forragem e de nutrientes. Os resultados apontaram que o manejo da oferta de forragem, mesmo modificando a abundância de forragem e determinando ambientes alimentares contrastantes, não permite controle estrito, tampouco predição, da estrutura do pasto, principalmente nos níveis moderados e altos de oferta de forragem (e.g., 12 e 16% PV). As relações demonstram que elevados níveis de consumo diário estão associados com o aumento na abundância de forragem e com a estrutura do pasto. Ofertas de forragem muito baixas ou altas podem comprometer a taxa de consumo de nutrientes. Elevado tempo de pastejo diário esteve associado com elevados deslocamentos, o que pode gerar maiores gastos energéticos. Os menores valores de tempo de pastejo diário estiveram associados às estruturas de pasto que apresentaram massa de forragem entre 1400-2200 kg de MS/ha e altura do pasto entre 8-13 cm, sendo que a ocorrência de touceiras não ultrapassou 35%. Já as condições de pasto que promoveram maiores consumo diário e elevada taxa de consumo foram observadas quando a oferta de forragem esteve em torno de 11% PV, situação em que a massa de forragem situava-se em 1800 kg de MS/ha, a altura do pasto encontrava-se em 11,9 cm e a presença de touceiras era de 30%. Dentro dessas amplitudes também se configurou elevado consumo de nutrientes, indicando que tais parâmetros caracterizam um ambiente pastoril desejável tanto do ponto de vista de bem-estar quanto em nível de produção animal. / The experiment was carried out at the Research Station of the Federal University of Rio Grande do Sul, Brazil, from Jan/2009 to Feb/2010, in order to assess the relationship of ingestive behaviour and forage intake with the daily herbage allowance and variables of sward structure aiming to define suitable environments to grazing on complex natural grassland. The usefulness for an acoustic method to assess the time of daily activities was studied, while for assessing dry matter intake the technique of alkanes from the theory of the double alkane was performed. A completely randomized block design with two replicates (paddocks) was used. The treatments were levels of daily herbage allowance applied since 1986: 4, 8, 12 and 16 kg DM/100 kg BW, or BW %. The experimental animals were crossbred heifers with 15 months of age and 152±4.0 kg that entered in the experimental area in Nov/2008. The variables used to describe the sward structure were: herbage mass, sward height and the frequency of tussocks. The variables of ingestive behaviour measured and used were: grazing time, displacement and daily displacement rate at grazing. The variables of daily intake studied were: the amount and rate of daily forage intake and nutrients. The results showed that the management of herbage allowance, even changing the abundance of forage and determining contrasting environments, does not allow for a strict control and prediction of sward structure, mainly for levels moderate to high of allowance. The relationships presented demonstrate that high levels of daily intake are associated with an increase in the abundance of forage and sward structure. Herbage allowance excessively low or high may provide lower intake rates of nutrients. High daily grazing time was associated with higher displacements, which can generate higher energy costs. The lowest values of daily grazing time was associated with structures that contained herbage mass between 1400-2200 kg DM/ha and sward height between 8-13 cm, whereas tussocks levels did not exceed 35%. The sward conditions that promoted high daily intake and high intake rate was observed when herbage allowance was around 11% BW, herbage mass was 1800 kg DM/ha, the sward height was 11,9 cm and the occurrence of tussocks of 30%. Within these ranges it has also become a high intake of nutrients indicating those parameters can characterize a suitable grazing environment both for animal welfare as well as for animal production aspects.