True prediction of lowest observed adverse effect levels

Summary A database of structurally heterogeneous chemical structures with their experimental values of Lowest Observed Adverse Effect Levels (LOAELs) was modeled using graph theoretical descriptors. Variable selection for multiple linear regression (MLR) and linear discriminant analysis (LDA) was accomplished by the Internal Test Set (ITS) method in order to achieve true predicted LOAEL values. The results obtained can be considered good if we take in count the structural diversity of the training set

Mechanism and Application of a Heterogeneous Catalytic Hydrogen-deuterium Exchange Reaction for Polyolefins

University of Minnesota Ph.D. dissertation. April 2018. Major: Chemical Engineering. Advisors: Frank Bates, Timothy Lodge. 1 computer file (PDF); xv, 135 pages.The mechanism of a heterogeneous catalytic H/D exchange reaction with polyolefins is investigated in this thesis. The model polymers used in this study were hydrogenated polybutadienes (hPBDs), and a metallocene linear low density polyethylene (LLDPE). When mixed at 170 ºC with isooctane, Pt/Re-SiO2 catalyst, and gaseous deuterium, the polyolefins dissolve and undergo H/D exchange reaction at the surface of the catalyst, producing partially deuterium labelled polyolefins. Polymers with varying molecular weight, varying ethyl branch density and narrow molecular weight distribution were synthesized by anionic polymerization of 1,3-butadiene followed by saturation with gaseous hydrogen. The LLDPE polymer with relatively broader molecular weight distribution is a commercial product and was supplied by ExxonMobil Chemical Company. The extent of deuterium labelling is analyzed with density measurement, proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared (FTIR) spectroscopy. A size exclusion chromatography (SEC) instrument equipped with an IR detector was used to analyze the deuterium concentration within the LLDPE polymer as a function of molecular weight. Small angle neutron scattering (SANS) was conducted for both the pure labelled polyolefins and their blends. The partially labelled LLDPE sample was fractionated according to the molecular weight. The partially labelled fractions were blended with the normal LLDPE to create samples with different molecular weight portions labelled. These labelled blends were uniaxially stretched at room temperature while simultaneously monitored with SANS, providing a method to characterize the single chain alignment process at different stages of polyethylene deformation, as a function of time. In this thesis, several aspects of the isotope exchange reaction were investigated. We first examined the dependence of the isotope exchange on the molecular weight and branch content of the substrate polyolefins. The extent of isotope exchange was found to strongly favor the high molecular weight molecules. High branch concentration hinders the exchange reaction, but has a less impact at low branch content. These observations are best explained by viewing the exchange reaction as an absorption controlled process. The deuterium distribution was found to be inhomogeneous evidenced by both the SEC-IR and SANS results. From SANS results modeling, it was confirmed that mathematical accommodation of the inhomogeneous deuterium distribution is necessary to extract chain statistics. Finally, the in situ tensile-SANS experiments revealed that the single chains develop a high degree of alignment along the stretching direction during the elastic and plastic deformation processes of the LLDPE, and maintain that alignment during the strain hardening regime. A remarkable higher degree of chain alignment was found for the high molecular weight chains, a result of longer chains being able to form more tie chains between lamellae. The results of this work provided a scheme of analyzing commercial polyolefins on the single molecular scale, without the necessity to access the synthesis route of the materials

Kinetic model construction using chemoinformatics

Kinetic models of chemical processes not only provide an alternative to costly experiments; they also have the potential to accelerate the pace of innovation in developing new chemical processes or in improving existing ones. Kinetic models are most powerful when they reflect the underlying chemistry by incorporating elementary pathways between individual molecules. The downside of this high level of detail is that the complexity and size of the models also steadily increase, such that the models eventually become too difficult to be manually constructed. Instead, computers are programmed to automate the construction of these models, and make use of graph theory to translate chemical entities such as molecules and reactions into computer-understandable representations. This work studies the use of automated methods to construct kinetic models. More particularly, the need to account for the three-dimensional arrangement of atoms in molecules and reactions of kinetic models is investigated and illustrated by two case studies. First of all, the thermal rearrangement of two monoterpenoids, cis- and trans-2-pinanol, is studied. A kinetic model that accounts for the differences in reactivity and selectivity of both pinanol diastereomers is proposed. Secondly, a kinetic model for the pyrolysis of the fuel “JP-10” is constructed and highlights the use of state-of-the-art techniques for the automated estimation of thermochemistry of polycyclic molecules. A new code is developed for the automated construction of kinetic models and takes advantage of the advances made in the field of chemo-informatics to tackle fundamental issues of previous approaches. Novel algorithms are developed for three important aspects of automated construction of kinetic models: the estimation of symmetry of molecules and reactions, the incorporation of stereochemistry in kinetic models, and the estimation of thermochemical and kinetic data using scalable structure-property methods. Finally, the application of the code is illustrated by the automated construction of a kinetic model for alkylsulfide pyrolysis

Nonmethane hydrocarbon chemistry in the remote marine atmosphere

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Vita.Includes bibliographical references (p. 169-173).by Neil McPherson Donahue.Ph.D

Anuário Científico – 2009 & 2010 Resumos de Artigos, Comunicações, Teses, Patentes, Livros e Monografias de Mestrado

O Conselho Técnico-Científico do Instituto Superior de Engenharia de Lisboa (ISEL), na senda da consolidação da divulgação do conhecimento e da ciência desenvolvidos pelo nosso corpo docente, propõe-se publicar mais uma edição do Anuário Científico, relativa à produção científica de 2009 e 2010. A investigação, enquanto vertente estratégica do Instituto Superior de Engenharia de Lisboa (ISEL), tem concorrido para o seu reconhecimento nacional e internacional como instituição de referência e de qualidade na área do ensino das engenharias. É também nesta vertente que o ISEL consubstancia a sua ligação à sociedade portuguesa e internacional através da transferência de tecnologia e de conhecimento, resultantes da sua atividade científica e pedagógica, contribuindo para o seu desenvolvimento e crescimento de forma sustentada. São parte integrante do Anuário Científico todos os conteúdos com afiliação ISEL resultantes de resumos de artigos publicados em livros, revistas e atas de congressos que os docentes do ISEL apresentaram em fóruns e congressos nacionais e internacionais, bem como teses e patentes. Desde 2002, ano da publicação da primeira edição, temos assistido a uma evolução crescente do número de publicações de conteúdos científicos, fruto do trabalho desenvolvido pelos docentes que se têm empenhado com afinco e perseverança. Contudo, nestes dois anos (2009 e 2010) constatou-se um decréscimo no número de publicações, principalmente em 2010. Uma das causas poderá estar diretamente relacionada com a redução do financiamento ao ensino superior uma vez que limita toda a investigação no âmbito da atividade de I&D e da produção científica. Na sequência da implementação do Processo de Bolonha em 2006, o ISEL promoveu a criação de cursos de Mestrado disponibilizando uma oferta educativa mais completa e diversificada aos seus alunos, mas também de outras instituições, dotando-os de competências inovadoras apropriadas ao mercado de trabalho que hoje se carateriza mais competitivo e dinâmico. Terminados os períodos escolar e de execução das monografias dos alunos, os resumos destas são igualmente parte integrante deste Anuário, no que concerne à conclusão dos Mestrados em 2009 e 2010.A fim de permitir uma maior acessibilidade à comunidade científica e à sociedade civil, o Anuário Científico será editado de ora avante em formato eletrónico. Excecionalmente esta edição contempla publicações referentes a dois anos – 2009 e 2010

FAA Center of Excellence for Alternative Jet Fuels & Environment: Annual Technical Report 2021: For the Period October 1, 2020 - September 30, 2021: Volume 2

FAA Award Number 13-C.This report covers the period October 1, 2020, through September 30, 2021. The Center was established by the authority of FAA solicitation 13-C-AJFE-Solicitation. During that time the ASCENT team launched a new website, which can be viewed at ascent.aero. The next meeting will be held April 5-7, 2022, in Alexandria, VA