• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 809
  • 233
  • 225
  • 76
  • 56
  • 30
  • 27
  • 24
  • 20
  • 18
  • 14
  • 8
  • 6
  • 6
  • 5
  • Tagged with
  • 1898
  • 297
  • 260
  • 236
  • 151
  • 145
  • 121
  • 117
  • 113
  • 112
  • 106
  • 94
  • 94
  • 92
  • 90
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

More Than A Curriculum: The Political Project of Radical Labour Education

Bonokoski, Nicholas 29 November 2011 (has links)
This thesis analyzes the experiences of participants of the Canadian Labour Congress and Saskatchewan Federation of Labour radical labour youth activist training program “Solidarity Works.” The theoretical work of Antonio Gramsci and Paulo Freire is used to analyze why radical labour education is important. The theoretical work of Michel Foucault is used, in addition to the work of Gramsci and Freire, to examine the complications of radical labour education. The essential argument of this thesis is that radical labour education programs like Solidarity Works produce an activist subjectivity that ultimately comes into conflict with the institutionalized politics of the labour movement. Solidarity Works is a model radical labour education project, its challenges and successes warrant analysis so those lessons can be used for future radical labour education projects.
92

Stable Free Radical Polymerization Conducted In Emulsion Polymerization Systems

Maehata, Hideo 22 February 2010 (has links)
Free radical polymerization is the most common polymerization technique that is used for the manufacturing of polymers, due to the ease of the polymerization initiation, wide latitude of the material design for a large variety of monomers, and the excellent process robustness for commercial production. In the 1990’s, research activities for the precise control of radical polymerization process resulted in the discovery of ‘Living Radical Polymerization’. The discoveries opened the door for the next generation of radical polymerizations. Extensive research has been conducted to understand the mechanisms and kinetics for numerous practical applications, particularly for polymerization in bulk and solution systems. However, despite the interest of industry, the mechanistic understanding in aqueous dispersed systems such as emulsion and miniemulsion polymerization is far behind the aforementioned two systems. There are still major challenges from the production viewpoint. One reason for the poor understanding is the complexity of the heterogeneous system, which includes multiple reaction phases that are accompanied by the segregation and transfer of the reaction species among different phases. The purpose of this research was to investigate living radical polymerization or “Stable Free Radical Polymerization” (SFRP) in aqueous dispersed systems to obtain better mechanistic understanding of how the heterogeneous nature of the system interacts with the novel living radical chemistry. The theoretical and experimental feasibility of the SFRP emulsion process were studied in this research, in particular, focusing on the compartmentalization effect. Particle size influence on the polymerization kinetics and the polymer livingness was experimentally confirmed, and compared to bulk polymerization. In addition, a comprehensive mathematical model including all major chemical and physical events was developed to further our mechanistic understanding. Based on the results from the experimental and modeling studies, it was shown that rate reduction in the smaller particles is the primary cause of difficulty in implementing a conventional emulsion process (i.e. ab initio emulsion polymerization). Finally, for overcoming this difficulty, a new approach using a combination of TEMPO with highly hydrophobic 4-stearoyl TEMPO was proposed for a coagulum free ab initio emulsion process. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-02-18 09:49:52.336
93

Controlled Radical Polymerization in the Dispersed Phase

Thomson, Mary 07 December 2010 (has links)
Controlled radical polymerization (CRP) has emerged as a powerful method of creating polymers with tailored molecular architectures under mild reaction conditions. However, production of these polymers efficiently at an industrial scale will likely require them to be synthesized in the dispersed phase. Three types of CRP are explored, Atom Transfer Radical Polymerization (ATRP), Nitroxide Mediated Polymerization (NMP) and Catalytic Chain Transfer (CCT) to elucidate the intricacies of creating these novel polymer colloids. Compartmentalization in an ATRP dispersed phase system is explored theoretically to understand the effects of particle size and catalyst concentration on the polymerization. The results suggest that there is an optimal range of particle sizes where the rate of polymerization is greater than that in an equivalent bulk system while maintaining both a lower PDI (polydispersity index) and higher livingness. All three factors are desirable in ATRP but generally cannot be achieved simultaneously in bulk. Compartmentalization manifests itself differently in CCT dispersed phase systems, where the segregation of the CCT agents into different polymer particles leads to multimodal molecular weight distributions. Control over the particle size is notoriously difficult for nitroxide mediated polymerization, as it is challenging to decouple an increase in the particle size with an increase in target molecular weight using a two stage emulsion polymerization approach. This often leads to colloidally unstable latexes for low molecular weight, high solids conditions which are the result of superswelling. We offer several strategies to minimize this problem and create colloidally stable, high solids, n-butyl acrylate latexes by NMP with moderate to high molecular weight targets (>70 kg/mol). Using this synergy between target molecular weight and particle size, high solids (>40 wt.%), high molecular weight (<200 kg/mol) microemulsions (~20 nm) of methyl methacrylate-co-styrene were prepared. Finally, the monomer type and nucleation mechanisms also play a role in determining the particle size distribution in NMP emulsion systems. Using n-butyl methacrylate in emulsion with surfactant concentrations above the critical micelle concentration yields latexes with bimodal particle size distributions. However a surfactant-free approach allows monomodal latexes to be created. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2010-12-03 13:30:15.346
94

Synthesis of benzo-fused nitrogen heterocycles and substituted benzenes

Ziffle, Vincent Unknown Date
No description available.
95

Development of new dendritic ligands for copper mediated Atom Transfer Radical Polymerization (ATRP) of methyl methacrylate.

Moni, Lucky. January 2008 (has links)
<p>&nbsp / </p> <p align="left">The main aim of this study was to design new polyfunctional ligands based on the polypropyleneimine dendrimer&nbsp / <font face="Arial">DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 <font face="Arial">referred to as </font><b><font face="Arial,Bold">L1 </font><font face="Arial">in this work, to be used in </font></b></font></font><font face="Arial">copper mediated atom transfer radical polymerization (ATRP) of vinyl monomers. These ligands were synthesized by modifying DAB-(NH</font><font face="Arial" size="1"><font face="Arial" size="1">2</font></font><font face="Arial">)</font><font face="Arial" size="1"><font face="Arial" size="1">4 </font></font><font face="Arial">with aromatic and aliphatic substituents on the nitrogen atoms at the periphery of </font><b><font face="Arial,Bold">L1</font><font face="Arial">.</font></b></p>
96

More Than A Curriculum: The Political Project of Radical Labour Education

Bonokoski, Nicholas 29 November 2011 (has links)
This thesis analyzes the experiences of participants of the Canadian Labour Congress and Saskatchewan Federation of Labour radical labour youth activist training program “Solidarity Works.” The theoretical work of Antonio Gramsci and Paulo Freire is used to analyze why radical labour education is important. The theoretical work of Michel Foucault is used, in addition to the work of Gramsci and Freire, to examine the complications of radical labour education. The essential argument of this thesis is that radical labour education programs like Solidarity Works produce an activist subjectivity that ultimately comes into conflict with the institutionalized politics of the labour movement. Solidarity Works is a model radical labour education project, its challenges and successes warrant analysis so those lessons can be used for future radical labour education projects.
97

Experimental and computational studies of DNA structure using the hydroxyl radical as a chemical probe

Greenbaum, Jason Adam January 2006 (has links)
Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / We have constructed a database of hydroxyl radical (•OH) cleavage patterns of DNA in order to investigate the relationship between the sequence of a DNA molecule and its three-dimensional structure. The hydroxyl radical cuts DNA at every nucleotide, with the amount of cutting proportional to the solvent accessible surface area (SASA) of the deoxyribose hydrogen atoms. Cleavage fragments are quantified by a fluorescence sequencer, followed by normalization and deposition into the database. Our database currently contains 151 DNA sequences with lengths ranging from 35 to 41 nucleotides. These data have enabled us to develop some general rules regarding the sequence-dependence of DNA structure as well as to predict the cleavage pattern of any given DNA sequence with remarkable precision. Using this prediction algorithm, it is possible to construct structural maps of entire genomes. As there are many examples of DNA binding proteins with highly degenerate binding sites, the use of structural information to locate these sites may be helpful. There also exists other signals, including the signal for nucleosome positioning, which have no apparent consensus, making it likely that the structure of DNA is of critical importance. We have developed algorithms to identify regions of conserved structure using •OH cleavage intensity as a proxy. Within a set of DNase I hypersensitive sites (DHS) obtained from the ENCODE Consortium, we were able to identify a stretch of 12 nucleotides for which the structural conservation is much greater than the sequence conservation. These sites have been dubbed Conserved •OH Radical Cleavage Signatures, or CORCS. Upon further analysis, these CORCS were found to be 17-fold enriched for DHS as compared to shuffled elements. Through the continued analysis of hydroxyl radical cleavage data and development of algorithms to employ the data in biologically meaningful ways, we hope to further our understanding of the relationship between DNA sequence and structure, and how the local structural heterogeneity of genomic DNA contributes to biological function. / 2031-01-02
98

Oxidative radical cyclisations for the synthesis of lactones

Martinez, Sandra Ainsua January 2017 (has links)
The object of study of this thesis lies on the optimisation of the oxidative radical cyclisation methodology for the preferential formation of gamma-lactones from unsaturated alkyl malonate derivatives. <strong>Chapter 1</strong> introduces the concept of free-radical cyclisation; more extensive explanations are given for the intramolecular oxidative radical cyclisation using manganese(III) and copper(II) salts as oxidants. An overview of the contribution of the Burton group in the field is given, in which both the applicability and the limitations of the transformation are showcased. <strong>Chapter 2</strong> is concerned with the synthesis of the ethisolide family of natural products and one non-natural analogue, in which the oxidative radical cyclisation is key for the construction of the bis-gamme-lactone moiety present in such natural products. The initial limitations of the methodology allowed for the discovery of new conditions for the formation of chloro monocyclic systems and for the development of copper-free oxidative cyclisation conditions for gamma-lactone formation. <strong>Chapter 3</strong> reports the developments on the metal-free oxidative radical cyclisation. Bicyclic gamma-lactones were synthesised from all-carbon alkyl malonate derivatives through anodic oxidation via constant current electrolysis. The development of a novel ionic oxidative cyclisation is also discussed. <strong>Chapter 4</strong> describes our efforts towards the formation of both fused and spiro gamma-lactam-beta-lactone molecules, as potential analogues to proteasome inhibitors, from either gamma-lactam-gamma-lactones or exo-gamma-lactams precursors, previously synthesised through oxidative radical cyclisation. Full experimental details, NMR spectra for the natural products and for the non-natural analogue, and a comparison between the obtained and the previously reported NMR data are also provided.
99

Aqueous ATRP of amine-based methacrylates

Malet, Federic Louis Gino January 2001 (has links)
No description available.
100

Intramolecular radical additions to aromatic compounds

Blumire, Nigel James January 2003 (has links)
This thesis is concerned with the development of cyclisation strategies that allow entry to polycyclic heterocycles and medium sized ring systems. Radical additions to pyridines are developed and methodologies explore the differences between the homolysis of C-Br and C-I bonds. Mechanisms are described for the unexpected ipso additions to the pyridines. Work towards the synthesis of the stegnans and dimethylgomisin illustrates the attempts to utilise the ipso addition to form medium sized ring systems. A new method of synthesising these medium sized ring systems is discussed. Progress towards a general methodology is described and shows the opportunities for which it could be utilised. A literature review of the synthesis of heterocycles via radical cyclisations is presented.

Page generated in 0.1016 seconds