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Polymer solutions in which there are strong specific interactions between the polymer and the solvent are of interest in a number of biological applications. Of particular interest are polymer solutions in which supercritical carbon dioxide (CO2) is the solvent, because polymer processing with CO2 is an important application of green chemistry. Unfortunately, experimental data on the phase behavior of polymer - CO2 systems are relatively scarce, as are models that describe the phase behavior of such systems. The focus of this research is therefore on developing a thermodynamic model based on lattice theory for calculating phase behavior of high pressure polymer solutions with specific intermolecular interactions. A new model, termed the LELAC (Lattice-based Extended Liquid Activity Coefficient) model is proposed based on the gART-L model of Sukhadia and Variankaval. The new model incorporates the compressibility effect at high pressures. The parameters of the model are (1) the equilibrium constant for association between a polymer segment and a solvent, (2) the specific interaction energy between a polymer segment and a solvent, and (3) the dispersion interaction energy. The dispersion interaction energy is calculated using Regular Solution Theory and therefore depends on the pure component properties. One or both of the remaining parameters is obtained from independent measurements such as FT- IR spectra. Alternatively, the two parameters can be obtained by fitting data. Cloud point curves of polymer - CO2 systems have been successfully correlated (1.3 % error) with the new model. Also, using fitted parameters from cloud point data, the sorption behavior of CO2 in polymers has been predicted. The polymer investigated include PBMA, PVAc and Polyacrylates. Comparison of cloud points with those obtained using the SAFT model revealed that the new model performs better than the SAFT model (3.6% error) with two adjustable parameters. The use of FT-IR to investigate interactions between CO2 and a number of polymers has been studied. The results confirm that complexes are formed between CO2 and PMMA, PEMA, PBMA, PVMK, and PVAc. A complex of PVC and CO2 is reported and a new mechanism involving a carbon oxygen triple bond is postulated for this system.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 155-168).

Gauge invariant shielding constants calculations of ?H, ?C, and ??N were calculated for acetonitrile in the gas and liquid phases. Dierent basis sets as well as dierent ab initio and DFT methods were tested to select a time-ecient level of theory with reasonable accuracy. The eect of nuclear motion on the shielding constants was also explored. To investigate solvent eects on the shielding constants of acetonitrile, dierent clusters were extracted from molecular dynamics simulations. Convergence to the experimental values varied for the dierent clusters. The geometry of the central molecule in a cluster played an important factor in reaching convergence. / Master of Science

Lam Chun Pong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / Table of Contents --- p.i / Acknowledgements --- p.v / Abstracts --- p.vi / Abbreviations --- p.viii / Chapter CHAPTER 1. --- SYNTHESIS AND REACTIVITY STUDIES OF MODEL COMPLEXES FOR INTRADIOL DIOXYGENASES WITH BENZIMIDAZOLE- CONTAINING LIGAND / Chapter I.1 --- Introduction / Chapter I.1.1 --- General Background --- p.1 / Chapter I.1.2 --- A General Review on the Modeling Chemistry for Catechol Dioxygenases --- p.3 / Chapter I.1.3 --- Intradiol Dioxygenases --- p.3 / Chapter I.1.3.1 --- Early model studies for intradiol dioxygenases --- p.5 / Chapter I.1.3.2 --- Factors affecting enzymatic reactivity for intradiol dioxygenases --- p.6 / Chapter I.1.3.3 --- Other functional models for intradiol dioxygenases --- p.7 / Chapter I.1.3.4 --- Reactivity studies of model complexes --- p.8 / Chapter I.1.4 --- Extradiol Dioxygenases --- p.8 / Chapter I.1.4.1 --- Early model studies for extradiol dioxygenases --- p.11 / Chapter I.1.4.2 --- Iron(III) complexes with extradiol properties --- p.12 / Chapter I.1.5 --- Objective of This Work --- p.14 / Chapter I.2 --- Results and Discussion / Chapter I.2.1 --- Synthesis of the Ligand Ntb --- p.15 / Chapter I.2.2 --- Synthesis of the Model Complex [Fe(ntb)Cl2]Cl --- p.16 / Chapter I.2.3 --- Synthesis of Enzyme-Substrate Model Complexes --- p.16 / Chapter I.2.4 --- Oxygenation Reactivities of Enzyme-Substrate Model Complexes 2-4 --- p.18 / Chapter I.2.4.1 --- Oxygenation of [Fe(ntb)(dbc)](C104) (2) in DMF --- p.18 / Chapter I.2.4.2 --- Oxygenation of [Fe(ntb)(cat)](Cl04) (3) in DMF --- p.21 / Chapter I.2.4.3 --- Oxygenation of [Fe(ntb)(tcc)](ClO4) (4) in DMF --- p.23 / Chapter I.2.4.4 --- Comparison of the oxygenation reactivities of complexes2-4 --- p.25 / Chapter I.2.5 --- Identification of Oxidative Cleavage Products --- p.27 / Chapter I.2.5.1 --- Isolation of oxidative cleavage products of complex 2 --- p.27 / Chapter I.2.5.2 --- Identification of cleavage products --- p.27 / Chapter I.2.6 --- Physical Characterization of Complexes 1-4 --- p.29 / Chapter I.2.6.1 --- Melting-points --- p.29 / Chapter I.2.6.2 --- Cyclic Voltammograms --- p.30 / Chapter I.2.6.3 --- EPR spectra --- p.31 / Chapter I.2.7 --- Molecular Structures of Complexes 1-4 --- p.34 / Chapter I.2.7.1 --- Molecular structure of [Fe(ntb)Cl2]Cl-4H20 (1) --- p.34 / Chapter I.2.7.2 --- Molecular structure of [Fe(ntb)(dbc)](Cl04)-2Me0H-H20 (2) --- p.36 / Chapter I.2.7.3 --- Molecular structure of [Fe(ntb)(cat)](ClO4) H20 (3) --- p.38 / Chapter I.2.7.4 --- Molecular structure of [Fe(ntb)(tcc)](Cl04).Me2C(0).H20 (4) --- p.41 / Chapter I.2.7.5 --- Comparison of the molecular structures of complexes 1-4 --- p.43 / Chapter I.3 --- Experimentals for Chapter 1 --- p.45 / Chapter I.4 --- References for Chapter 1 --- p.49 / Chapter CHAPTER II --- iron(iii) complexes containing N202 and N3O type ligands as models for INTRADIOL DIOXYGENASES / Chapter II.1 --- Introduction / Chapter II.1.1 --- Brief Remarks on Model Studies of Intradiol Dioxygenases. --- p.53 / Chapter II.1.2 --- Objective of This Work --- p.53 / Chapter II.2 --- Results and Discussion / Chapter II.2.1 --- Synthesis of N202 and N30 Type Ligands --- p.55 / Chapter II.2.2 --- Synthesis of Model Complexes --- p.57 / Chapter II.2.2.1 --- Model complex with ligand L1H --- p.57 / Chapter II.2.2.2 --- Model complex with ligand L2H2 --- p.58 / Chapter II.2.3 --- Synthesis of Enzyme-Substrate Model Complexes --- p.59 / Chapter II.2.3.1 --- Synthesis of enzyme-substrate model complexes from 14.… --- p.59 / Chapter II.2.3.2 --- Attempted synthesis of enzyme-substrate model complexes starting from 15 --- p.61 / Chapter II.2.4 --- Reaction of Complex 16 with Dioxygen --- p.61 / Chapter II.2.4.1 --- Oxygenation of [Fe(L1)(dbc)] (16) in DMF --- p.65 / Chapter II.2.5 --- Identification of Oxidative Cleavage Products --- p.64 / Chapter II.2.5.1 --- Isolation of oxidative cleavage products of complex 16 --- p.64 / Chapter II.2.5.2 --- Identification of cleavage products --- p.65 / Chapter II.2.6 --- "Physical Characterization of L1H, L2H2, Complexes 14-18" --- p.66 / Chapter II.2.6.1 --- NMR spectra --- p.67 / Chapter II.2.6.2 --- Melting-points --- p.69 / Chapter II.2.6.3 --- Mass spectra --- p.69 / Chapter II.2.6.4 --- Cyclic voltammogram --- p.69 / Chapter II.2.6.4 --- EPR spectra --- p.70 / Chapter II.2.7 --- "Molecular Structures of Complexes 14,15 and 18" --- p.71 / Chapter II.2.7.1 --- Molecular structure of [Fe(L1)(MeOH)Cl][BPh4].MeOH (14) --- p.72 / Chapter II.2.7.2 --- Molecular structure of [Fe(L2)Cl].MeOH (15) --- p.75 / Chapter II.2.7.3 --- Molecular structure of [Et3 Nh]3［Fe(tcc)3］.H2O(18) --- p.78 / Chapter II.3 --- Experimentals for Chapter 2 --- p.80 / Chapter II.4 --- References for Chapter 2 --- p.87 / APPENDIX 1 General Procedures and Physical Measurements --- p.89 / "APPENDIX 2 Selected Crystallographic Data for Complexes 1-4, 15,16 and 18.…" --- p.90 / Table A-l.Selected crystallographic data for complexes 1-4 --- p.91 / "Table A-2.Selected crystallographic data for complexes 15, 16 and 18" --- p.92 / "APPENDIX 3 Other Physical Data for Ligand L1H L2H2, Complexes 2 and 16" --- p.93 / Figure A-l.1H NMR spectrum of ligand L1H --- p.94 / Figure A-2.13C NMR spectrum of ligand L1H --- p.94 / Figure A-3.1H NMR spectrum of ligand L2H2 --- p.95 / Figure A-4.13C NMR spectrum of ligand L2H2 --- p.95 / Figure A-5.GC spectrum of the oxidative cleavage products of complex 2 --- p.96 / Figure A-6.- A-l 1.Mass spectra of the oxidative cleavage products of Complex 2 --- p.96 / Figure A-12.GC spectrum of the oxidative cleavage products of complex 16 --- p.99 / Figure A-13.- A-23.Mass spectra of the oxidative cleavage products of Complex 16 --- p.99 / Figure A-24.GC spectrum of dbcH2 standard --- p.105 / Figure A-25.Mass spectrum of dbcH2 standard --- p.106 / Figure A-26.GC spectrum of dbcq standard --- p.106 / Figure A-27.Mass spectrum of dbcq standard --- p.107

Thesis (Ph. D.)--Institute of Paper Chemistry, 1952. / Includes bibliographical references (p. 71-72).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 122-138).

Α three-dimensional chemical transport model (PMCAMx) is used to simulate particulate matter (PM) mass and composition in the eastern United States during the four seasons of the year (July 2001, October 2001, January 2002, and April 2002). The model predictions are evaluated against daily average PM2.5 (particulate mass less than 2.5 micrometers) measurements taken throughout the eastern United States by the Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Speciation Trends Network (STN) monitoring networks and the U.S. Environmental Protection Agency EPA Supersites program. During the spring and summer the model reproduces the measured daily average PM2.5 concentrations with an error of less than 50%, two thirds of the time. The PM2.5 error is less than 30% for 43% of the measurements during these seasons. For the fall and winter the PM2.5 predictions are within 50% of the measurements for 51% of the data points and within 30% for 34% of the time. The ability of the model to reproduce the aerosol nitrate concentrations in the spring and summer is limited by difficulties in simulating the heterogeneous nighttime formation rate of nitric acid. An important limitation of thισ model is the lack of treatment of crustal species (Ca, K, Mg, etc.). The incorporation of the thermodynamics of the crustal elements of calcium, potassium and magnesium to the preexisting suite of components of PMCAMx is the second objective of this research. The improved PMCAMx is applied to the Mexico City Metropolitan Area (MCMA). The aerosol thermodynamic model ISORROPIA-II is used to explicitly simulate the effect of Ca, Mg, and K from dust on semi-volatile partitioning and water uptake. The hybrid approach is applied to simulate the inorganic components, assuming that the smallest particles are in thermodynamic equilibrium, while describing the mass transfer to and from the larger ones. The final objective of this research is to provide useful information about the response of the PM concentration levels to changes in emissions. PMCAMx is used to investigate changes in PM2.5 concentrations in response to changes in SO2 and NH3 emissions during July 2001 and January 2002 in the Eastern United States. / Ένα τρισδιάστατο μοντέλο χημικής μεταφοράς (PMCAMx) χρησιμοποιήθηκε για την προσομοίωση της σύνθεσης και της μάζας των ανόργανων σωματιδίων της ατμόσφαιρας στις ανατολικές Ηνωμένες Πολιτείες της Αμερικής κατά τη διάρκεια των τεσσάρων εποχών του χρόνου (Ιούλιος 2001, Οκτώβρης 2001, Ιανουάριος 2002 και Απρίλιος 2002). Οι προβλέψεις του μοντέλου αξιολογήθηκαν έναντι μετρήσεων που πραγματοποιήθηκαν από τα δίκτυα παρακολούθησης IMPROVE και STN στις ανατολικές ΗΠΑ. Την άνοιξη και το καλοκαίρι το μοντέλο αναπαράγει τα δύο τρίτα των μετρήσεων των μικρών σωματιδίων (διαμέτρου μικρότερης των 2.5 μm, PM2.5) με σφάλμα μικρότερο του 50%. Το σφάλμα που προκύπτει για τα PM2.5 είναι μικρότερο του 30% για το 43% των μετρήσεων κατά τη διάρκεια των ίδιων εποχών. Για το φθινόπωρο και το χειμώνα οι προβλέψεις του μοντέλου για τα PM2.5 είναι μέσα στα όρια σφάλματος του 50% από τις μετρήσεις για το 51% των δεδομένων και μέσα στα όρια σφάλματος του 30% για το 34% των περιπτώσεων. Η απόδοση του μοντέλου, όσον αφορά τα νιτρικά ιόντα, βελτιώθηκε σημαντικά μετά τις τροποποιήσεις που εφαρμόστηκαν στην περιγραφή της αέριας χημείας κατά τη διάρκεια της νύχτας. Μια σημαντική έλλειψη σε αυτό το μοντέλο είναι η περιγραφή του χημικού ρόλου των σωματιδίων της σκόνης στην ατμόσφαιρα. Το θερμοδυναμικό μοντέλο ISORROPIA αναβαθμίστηκε έτσι ώστε να μπορεί να προσομοιώνει λεπτομερώς την χημεία των αλάτων ασβεστίου, μαγνησίου και καλίου, και ενσωματώθηκε σε αυτό το τρισδιάστατο χημικό μοντέλο. Επίσης, το PMCAMx εμπεριέχει διεργασίες για την ανάπτυξη των ανόργανων σωματιδίων και τη χημεία στην υγρή φάση. Επιπλέον, εφαρμόστηκε μία υβριδική προσέγγιση για τη μοντελοποίηση της δυναμικής των αιωρούμενων σωματιδίων έτσι ώστε να προσομοιωθούν με ακρίβεια τα ανόργανα συστατικά στα μεγάλα σωματίδια (διαμέτρου 2.5-10 μm). Σε αυτή τη περίπτωση το PMCAMx εφαρμόστηκε στην ευρύτερη περιοχή της πόλης του Μεξικού καλύπτοντας μία έκταση 156x156x6 km. Τέλος το PMCAMx έχει χρησιμοποιηθεί για να μελετηθούν διεξοδικά οι αλλαγές στη συγκέντρωση των PM2.5 που προκύπτουν από αλλαγές των εκπομπών SO2 και NH3 κατά τη διάρκεια των μηνών Ιούλιος 2001 και Ιανουάριος 2002 στις ανατολικές Ηνωμένες Πολιτείες της Αμερικής.

Objects can be said to be structured when their representation also contains their parts. While OWL in general can describe structured objects, description graphs are a recent, decidable extension to OWL which support the description of classes of structured objects whose parts are related in complex ways. Classes of chemical entities such as molecules, ions and groups (parts of molecules) are often characterised by the way in which the constituent atoms of their instances are connected via chemical bonds. For chemoinformatics tools and applications, this internal structure is represented using chemical graphs. We here present a chemical knowledge base based on the standard chemical graph model using description graphs, OWL and rules. We include in our ontology chemical classes, groups, and molecules, together with their structures encoded as description graphs. We show how role-safe rules can be used to determine parthood between groups and molecules based on the graph structures and to determine basic chemical properties. Finally, we investigate the scalability of the technology used through the development of an automatic utility to convert standard chemical graphs into description graphs, and converting a large number of diverse graphs obtained from a publicly available chemical database. / Computer Science (School of Computing) / M. Sc. (Computer Science)

The literature review shows that student alternative conceptions or misconceptions are important for teaching and learning. Causes of such student difficulties may include the counter-intuitive nature of some chemistry concepts or to instruction itself. However, over 30 years research into student conceptual difficulties has had little impact on teaching and learning chemistry. In this study, a critical analysis and synthesis of published research into student conceptions in acid-base chemistry was carried out in the naturalist nomothetic paradigm using a constructivist framework. Historical models which were included were an operational macroscopic model and the theoretical Arrhenius and Brønsted models. Firstly, a comprehensive search strategy with defined inclusion/exclusion criteria identified 42 suitable reports which were mostly peer-reviewed. The identified research was not limited to Anglophone countries although Africa and South America were underrepresented and research among secondary students predominated. Then a critique of the research showed it was of variable quality and often poorly reported. An outcome was a set of guidelines for research into student conceptions. The variable quality and reporting of research then also necessitated a four-level framework to reflect the stability of descriptions of student difficulties. A new method for synthesis of descriptions of student conceptual difficulties was developed which entailed mapping qualitative data on the difficulties, which had been extracted from research publications, to propositional knowledge statements derived in this study. This was an iterative process which simultaneously honed descriptions of difficulties and illuminated propositional knowledge implicated in them. The second major outcome was synthesized descriptions of 10 student difficulties with acid-base species, 26 difficulties with acid-base properties and 17 difficulties concerning terminology and symbolism particular to acid-base chemistry. Some conceptions were also found to have been mis-reported as ‘misconceptions’. The difficulties could be broadly due to student conceptions concerning acid-base models, or students not relating empirical observations to theoretical models or their poor understanding of underlying chemical principles. Some difficulties were found to have been over-researched, while further work was needed to clarify the nature some difficulties with conceptions of bases, acid-base reactions, and symbolism used in acid-base chemistry. The third major outcome from the synthesis was 218 propositional knowledge statements which were shown to be suitable for teaching high-school students, avoided hybrid historical models and were acceptable to expert chemists. These propositional statements were integrated as a set of 11 concept maps. The maps showed the hierarchy and interconnectedness of concepts as well as the propositional links which had been implicated in the difficulties. Furthermore the concept maps indicated critical concepts where teaching in each topic should focus as well as cross-linked concepts that can be used to integrate different aspects of the topic. Accordingly they contribute to PCK in the acidbase topic as they represent the fine-grained yet well integrated conceptual knowledge characteristic of a teacher with highly developed PCK. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.