Fitting ideals and module structure

Let R be a commutative ring with a 1. Original work by H. Fitting showed how we can associate to each finitely generated E-module a unique sequence of R-ideals, which are known as Fitting Ideals. The aim of this thesis is to undertake an investigation of Fitting Ideals and their relation with module structure and to construct a notion of Fitting Invariant for certain non-commutative rings. We first of all consider the commutative case and see how Fitting Ideals arise by considering determinantal ideals of presentation matrices of the underlying module and we describe some applications. We then study the behaviour of Fitting Ideals for certain module structures and investigate how useful Fitting Ideals are in determining the underlying module. The main part of this work considers the non-commutative case and constructs Fitting Invariants for modules over hereditary orders and shows how, by considering maximal orders and projectives in the hereditary order, we can obtain some very useful invariants which ultimately determine the structure of torsion modules. We then consider what we can do in the non-hereditary case, in particular for twisted group rings. Here we construct invariants by adjusting presentation matrices which generalises the previous work done in the hereditary case

Passive permeation in model biological membranes

The subject of this thesis is the study of mass transport using experimental and theoretical techniques, specifically the investigation of transport through phospholipid barriers which serve as a model for biological systems. To this end, experimental monolayer and bilayer membranes are produced, and the permeation of gas and weak acid molecules is quantitatively measured. Potentiostatic measurement of oxygen permeation in monolayers formed using two varieties of phospholipid at the air/water interface, under varying levels of compression (and hence surface pressure), was performed using ultramicroelectrodes, followed by finite element simulations to parameterise the approach curves produced and hence determine the first-order rate constant for the permeation process. As expected, the rate of permeation decreases significantly as the monolayers are compressed, with a simple surface pressure model proving insufficient to describe these trends. Molecular dynamics simulations are employed to investigate the excess free energy barriers for permeating oxygen molecules using umbrella sampling and the weighted histogram analysis method. The results are shown to be unreliable in their description of the permeation process. Experimental bilayers are formed from lecithin, pure POPC, and a mixture of POPC and cholesterol in a supporting electrolyte solution. The permeation of a homologous series of protonated weak acids is studied using laser scanning confocal microscopy to selectively excite and detect the state of fluorescein, a dye with pH-sensitive fluorescence intensity. These experimental results are again parameterised with finite element models, and the trend of decreasing permeation coefficient as the weak acid molecules increase in size is reported. This is in direct contradiction to the established Overton’s Rule. Molecular dynamics simulations of the permeation of three of the weak acids in a POPC bilayer is performed to determine excess free energy profiles using umbrella sampling, combined with the weighted histogram analysis method. Serious flaws are found in the method and execution of this aspect of the work

Passive permeation in model biological membranes

The subject of this thesis is the study of mass transport using experimental and theoretical techniques, specifically the investigation of transport through phospholipid barriers which serve as a model for biological systems. To this end, experimental monolayer and bilayer membranes are produced, and the permeation of gas and weak acid molecules is quantitatively measured. Potentiostatic measurement of oxygen permeation in monolayers formed using two varieties of phospholipid at the air/water interface, under varying levels of compression (and hence surface pressure), was performed using ultramicroelectrodes, followed by finite element simulations to parameterise the approach curves produced and hence determine the first-order rate constant for the permeation process. As expected, the rate of permeation decreases significantly as the monolayers are compressed, with a simple surface pressure model proving insufficient to describe these trends. Molecular dynamics simulations are employed to investigate the excess free energy barriers for permeating oxygen molecules using umbrella sampling and the weighted histogram analysis method. The results are shown to be unreliable in their description of the permeation process. Experimental bilayers are formed from lecithin, pure POPC, and a mixture of POPC and cholesterol in a supporting electrolyte solution. The permeation of a homologous series of protonated weak acids is studied using laser scanning confocal microscopy to selectively excite and detect the state of fluorescein, a dye with pH-sensitive fluorescence intensity. These experimental results are again parameterised with finite element models, and the trend of decreasing permeation coefficient as the weak acid molecules increase in size is reported. This is in direct contradiction to the established Overton’s Rule. Molecular dynamics simulations of the permeation of three of the weak acids in a POPC bilayer is performed to determine excess free energy profiles using umbrella sampling, combined with the weighted histogram analysis method. Serious flaws are found in the method and execution of this aspect of the work.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Taking Development Seriously: Critique of the 2008 \u3ci\u3eJME\u3c/i\u3e Special Issue on Moral Functioning

This essay comments on articles that composed a Journal of Moral Education Special Issue (September, 2008, 37[3]). The issue was intended to honor the 50th anniversary of Lawrence Kohlberg’s doctoral dissertation and his subsequent impact on the field of moral development and education. The articles were characterized by the issue editor (Don Collins Reed) as providing a “look forward” from Kohlberg’s work toward a more comprehensive or integrated model of moral functioning. Prominent were culturally pluralist and biologically based themes, such as cultural learning; expert skill; culturally shaped and neurobiologically based predispositions or intuitions; and moral self-relevance or centrality. Inadequately represented, however, was Kohlberg’s (and Piaget’s) key concept of development as the construction of a deeper or more adequate understanding not reducible to particular socialization practices or cultural contexts. Also neglected were related cognitive-developmental themes, along with supportive evidence. Robert Coles’s account of a sudden rescue is used as a heuristic to depict Piaget’s/Kohlberg’s approach to the development of moral functioning. We conclude that, insofar as the Special Issue does not take development seriously, it moves us not forward but, instead, back to the problems of moral relativism and moral paralysis that Kohlberg sought to redress from the start of his work more than 50 years ago

Drivers of vegetation change in grasslands of the Sheffield region, northern England, between 1965 and 2012/13

Questions: How has vegetation species diversity and species composition changed between 1965 and 2012/13 in acidic and calcareous grasslands? What has driven this change in vegetation? Location: A 2400-km2 area around Sheffield, northern England. Methods: In 1965 a survey was conducted to describe grassland vegetation of the Sheffield region. We repeated this survey in 2012/13, revisiting acidic and calcareous grassland sites (455 quadrats). Climate, N and sulphur deposition, cattle and sheep stocking rates, soil pH, altitude, aspect and slope were considered to be potential drivers of variation in vegetation. We analysed temporal changes in vegetation and examined relationships with spatial and temporal variation in driver variables. Results: Both acidic and calcareous grasslands showed clear changes in species composition between the two time periods. In acidic grasslands there was no significant change in richness but there were declines in diversity. There were significant increases in Ellenberg N. Nitrogen deposition and grazing were identified as potential drivers of spatial and temporal patterns but it was not possible to discriminate the respective impacts of potential drivers. In calcareous grasslands there were declines in species richness, diversity and appropriate diversity indices. Climate and soil pH were identified as potential drivers of spatial and temporal patterns. Conclusions: Despite only small site losses compared to other surveys in the UK, especially within the national park, both calcareous and acidic grasslands showed very clear changes in species composition. In acidic grasslands, high abundance of Pteridium aquilinum was a particular problem and had increased considerably between the two survey periods. Atmospheric N deposition and grazing were identified as drivers of species diversity. A number of calcareous grasslands showed signs of reduced management intensity leading to scrub invasion

Coarse-grained simulation reveals key features of HIV-1 capsid self-assembly

The maturation of HIV-1 viral particles is essential for viral infectivity. During maturation, many copies of the capsid protein (CA) self-assemble into a capsid shell to enclose the viral RNA. The mechanistic details of the initiation and early stages of capsid assembly remain to be delineated. We present coarse-grained simulations of capsid assembly under various conditions, considering not only capsid lattice self-assembly but also the potential disassembly of capsid upon delivery to the cytoplasm of a target cell. The effects of CA concentration, molecular crowding, and the conformational variability of CA are described, with results indicating that capsid nucleation and growth is a multi-stage process requiring well-defined metastable intermediates. Generation of the mature capsid lattice is sensitive to local conditions, with relatively subtle changes in CA concentration and molecular crowding influencing self-assembly and the ensemble of structural morphologies

Coarse-grained simulation of transmembrane peptides in the gel phase

We use Dissipative Particle Dynamics simulations, combined with parallel tempering and umbrella sampling, to investigate the potential of mean force between model transmembrane peptides in the various phases of a lipid bilayer, including the low-temperature gel phase. The observed oscillations in the effective interaction between peptides are consistent with the different structures of the surrounding lipid phases

Coarse-grained simulation reveals key features of HIV-1 capsid self-assembly

The maturation of HIV-1 viral particles is essential for viral infectivity. During maturation, many copies of the capsid protein (CA) self-assemble into a capsid shell to enclose the viral RNA. The mechanistic details of the initiation and early stages of capsid assembly remain to be delineated. We present coarse-grained simulations of capsid assembly under various conditions, considering not only capsid lattice self-assembly but also the potential disassembly of capsid upon delivery to the cytoplasm of a target cell. The effects of CA concentration, molecular crowding, and the conformational variability of CA are described, with results indicating that capsid nucleation and growth is a multi-stage process requiring well-defined metastable intermediates. Generation of the mature capsid lattice is sensitive to local conditions, with relatively subtle changes in CA concentration and molecular crowding influencing self-assembly and the ensemble of structural morphologies