Thesis (M.A.)--University of North Carolina at Chapel Hill, 2004. / Includes bibliographical references (leaves 119-123).

Thesis (M.A.)--University of North Carolina at Chapel Hill, 2004. / Includes bibliographical references (leaves 105-109).

Thesis (M.S.)--West Virginia University, 2005. / Includes bibliographical references. Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (M.S.)--West Virginia University, 2005. / Includes bibliographical references.

The transportation of mass is an inherently `non-equilibrium' process, relying on a current of mass between two or more locations. Life exists by necessity out of equilibrium and non-equilibrium transport processes are seen at all levels in living organisms, from DNA replication up to animal foraging. As such, biological processes are ideal candidates for modelling using non-equilibrium stochastic processes, but, unlike with equilibrium processes, there is as of yet no general framework for their analysis. In the absence of such a framework we must study specific models to learn more about the behaviours and bulk properties of systems that are out of equilibrium. In this work I present the analysis of three distinct models of non-equilibrium mass transport processes. Each transport process is conceptually distinct but all share close connections with each other through a set of fundamental nonequilibrium models, which are outlined in Chapter 2. In this thesis I endeavour to understand at a more fundamental level the role of stochasticity and fluctuations in non-equilibrium transport processes. In Chapter 3 I present a model of a diffusive search process with stochastic resetting of the searcher's position, and discuss the effects of an imperfection in the interaction between the searcher and its target. Diffusive search process are particularly relevant to the behaviour of searching proteins on strands of DNA, as well as more diverse applications such as animal foraging and computational search algorithms. The focus of this study was to calculate analytically the effects of the imperfection on the survival probability and the mean time to absorption at the target of the diffusive searcher. I find that the survival probability of the searcher decreases exponentially with time, with a decay constant which increases as the imperfection in the interaction decreases. This study also revealed the importance of the ratio of two length scales to the search process: the characteristic displacement of the searcher due to diffusion between reset events, and an effective attenuation depth related to the imperfection of the target. The second model, presented in Chapter 4, is a spatially discrete mass transport model of the same type as the well-known Zero-Range Process (ZRP). This model predicts a phase transition into a state where there is a macroscopically occupied `condensate' site. This condensate is static in the system, maintained by the balance of current of mass into and out of it. However in many physical contexts, such as traffic jams, gravitational clustering and droplet formation, the condensate is seen to be mobile rather than static. In this study I present a zero-range model which exhibits a moving condensate phase and analyse it's mechanism of formation. I find that, for certain parameter values in the mass `hopping' rate effectively all of the mass forms a single site condensate which propagates through the system followed closely by a short tail of small masses. This short tail is found to be crucial for maintaining the condensate, preventing it from falling apart. Finally, in Chapter 5, I present a model of an interface growing against an opposing, diffusive membrane. In lamellipodia in cells, the ratcheting effect of a growing interface of actin filaments against a membrane, which undergoes some thermal motion, allows the cell to extrude protrusions and move along a surface. The interface grows by way of polymerisation of actin monomers onto actin filaments which make up the structure that supports the interface. I model the growth of this interface by the stochastic polymerisation of monomers using a Kardar-Parisi-Zhang (KPZ) class interface against an obstructing wall that also performs a random walk. I find three phases in the dynamics of the membrane and interface as the bias in the membrane diffusion is varied from towards the interface to away from the interface. In the smooth phase, the interface is tightly bound to the wall and pushes it along at a velocity dependent on the membrane bias. In the rough phase the interface reaches its maximal growth velocity and pushes the membrane at this speed, independently of the membrane bias. The interface is rough, bound to the membrane at a subextensive number of contact points. Finally, in the unbound phase the membrane travels fast enough away from the interface for the two to become uncoupled, and the interface grows as a free KPZ interface. In all of these models stochasticity and fluctuations in the properties of the systems studied play important roles in the behaviours observed. We see modified search times, strong condensation and a dramatic change in interfacial properties, all of which are the consequence of just small modifications to the processes involved.

Acute lower body exercise elicits adverse effects on balance performance and subsequent fall risk. However, little information exists for upper body exercise and postural sway. The series of experimental studies presented in this thesis investigated the effects of acute upper and lower body exercise on postural sway in healthy young and older adults and determined whether the acute negative effects of exercise can be removed by an improvement in training status. Chapter 4 examined the effects of maximal and submaximal (absolute and relative exercise intensities) arm crank ergometry (ACE) and cycle ergometry (CE) on postural sway in young healthy adults. Cycling elicited an immediate increase in post exercise postural sway whereas ACE did not. Chapter 5 compared the effects ACE, CE and treadmill walking (TM) on postural sway in healthy older adults. Based on the findings of Study 1, submaximal exercise was performed at the same relative intensity (50 % HRE). In agreement with Chapter 4, CE and TM elicited post exercise balance impairments lasting for ~ 10 min post exercise. ACE performed at the same relative intensity as the lower body did not elicit post exercise balance impairments in older adults. Collectively, these acute studies suggest that lower limb exercise may acutely increase fall and injury risk in the immediate period after exercise cessation. This is important because practitioners and clinicians should acknowledge that the prescription of conventional training modes might potentially elicit transient impairments in neuromuscular function. However, in this context it appears that seated exercise with the arms may not induce a significant enough stimulus to cause sensorimotor disturbance to postural stability and thus may be a safer alternative exercise mode for fall risk populations or individuals who are very sedentary. Chapter 6 examined differences in balance performance, as measured by quantitative posturography and functional balance tests, among different age groups. Measures of postural sway were able to distinguish between younger (< 60 years) and older ( > 60 years) adults whereas functional performance tests suggested that balance impairments were observed earlier ( > 50 years). This study enabled a range of tests to be determined for use with subsequent training interventions. Chapter 7 examined the effects of 6-weeks upper or lower body exercise training on postural sway. Upper and lower body training elicited similar improvements in specific (~ 25 %) and cross transfer (~ 12 %) exercise tolerance. Both modes of training elicited favourable balance adaptations. Specifically, upper body training improved mediolateral aspects of postural sway, while lower body training improved anteroposterior aspects of sway. It was proposed that an improvement in cross transfer exercise capacity after upper body exercise reduced the physiological strain experienced during CE, thus reducing post exercise balance impairments and that an increase in abdominal and trunk strength from upper body exercise training reduced sway following ACE. Importantly, ACE also elicited an improvement in functional reach distance and timed up and go test speed. Conversely, CE improved lower limb strength which elicited an improvement in lower body dynamic balance. It is likely that engaging in both upper and lower body exercise will be better that either mode of exercise alone for both health and fitness and balanced incorporated in everyday life. ACE elicits a number of significant benefits to cardiovascular fitness and balance which is important for a number of older subgroups who might have difficulty engaging in lower limb exercise, such as those who are very sedentary, those with lower limb injury/disease or undergoing surgery rehabilitation and individuals who are overweight. Specifically, ACE may offer a pathway from sedentary living to physical activity. Upper body endurance exercise can contribute to a multimodal training stimulus by eliciting favourable adaptations in fitness, functional performance and balance. Such responses are important because this type of exercise may serve a feasible and time-efficient training regime for older adults, which will likely result in improved attrition and adherence to physical activity.

No description available.

From Introduction: It is now nearly 50 years since the appearance of Keynes's General Theory of Employment, Interest and Money and the stream of articles and books on what Keynes really meant or didn't mean shows no sign of abating. In part, this dissertation is a contribution to this voluminous literature, but what follows is hardly an attempt to provide an exhaustive interpretation. Instead the General Theory is examined from a certain angle, with the title "Equilibrium, Expectations and Information" providing the framework for the investigation. That the title has been borrowed from G.B. Richdrdson's 1959 Economic Journal article is no accident. Richardson's work has been unduly neglected and his trichotomy serves as a convenient platform from which to analyse Keynes's method and those of his interpreters, in particular the approaches stemming from the work of Clower and Leijonhufvud. The information structure of the Walrasian type of general equilibrium model is also examined as the latter forms the basis of both the neo-classical interpretation of Keynes's contribution and the rational expectations approach that will be discussed. Finally Richardson's framework is applied in an analysis of two modern classical schools of thought, namely the rational expectations approach headed by Lucas, and the neoRicardian school amongst which Garegnani, Eatwell and Milgate, for example, are prominent. In a sentence, therefore, what follows is an examination of the General Theory and certain interpretations thereof as well as an analysis of modern classical macroeconomics, with the equilibrium-expectations-information framework providing the unifying theme. As will become apparent, the framework does not consist of three watertight compartments. For example, whether a system is in equilibrium or not will depend on whether the expectations of those who have the ablility to effect change are realised. The specification of which agents have this power will depend on the information with which the model builder endows the agents in the model. In discussing this, attention is drawn to Keynes's important distinction between an entrepreneur economy and a cooperative economy. The distinction between the information available to the model builder and that with which he endows the agents in the model is also emphasized.

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

Using α-cyanostilbenes as Lewis acids, Lewis acidity scales have been established in the systems DMSO-ethanol and DMSO-methanol containing the appropriate 0.01M sodium alkoxide and in the system sodium methoxide-methanol. This scale, designated HR-, describes the ability of the solvent to add an alkoxide ion to an alkene. The HR- values range from 11.73 in methanol to 21.74 in 93.27 mole % DMSO in ethanol. The most acidic indicator used to establish the scale was α-cyano-2,4-dinitrostilbene with a pK of 12.73 in DMSO-methanol. The least acidic was α-cyano-3-trifluoromethylstilbene with a pK of 21.98 in DMSO-ethanol. The effects of substituents in the two aromatic rings of α-cyanostilbenes on the Lewis acidity of these compounds has been measured. Using Ϭ values, an average ρ of 2.2 was obtained for the β -phenyl ring in the various solvent systems studied. Using Ϭˉ values, the ρ for α-cyanostilbenes with substituents in the α-ring is 4.77 in DMSO-ethanol and 4.24 in DMSO-methanol. In the α-phenyl ring the 4-nitro group exhibits a greatly exalted sigma value (1.75). In order to compare the HR- and H_ scales in one system, the H_ scale has been established in sodium methoxide-methanol using various carbon acids as indicators. The two scales are nearly parallel. The rates of the base catalyzed isomerization of α-eyano-cis-stilbenes were found to correlate with the HR- function. Plots of the logarithms of the apparent first order rate constants (k₁) for the isomerization against the HR- values gave excellent straight lines with slopes ranging from 0.426 to 0.665. The slopes of these lines depend on the substituent present in the α-phenyl ring and on the solvent system. The slopes were shown to be a measure of how closely the transition state for the isomerization reaction resembles the carbanion formed by the equilibrium addition of alkoxide ion to an alkene. The effect of substituents on the rate of isomerization of α-cyano-cis-stilbenes has been determined. Using Ϭ values the ρ for substituents in the α-phenyl ring is 3.07 in DMSO-ethanol and 2.82 in DMSO-methanol. The activation parameters for the base catalyzed isomerization reaction have been determined in DMSO-methanol. The enthalpies of activation range from 14.3 to 16.7 kcal. mole⁻¹ and the entropies of activation range from -9.3 to -13.7 e.u. depending on the substituent. The base catalyzed isomerization of α-cyano-cis-stilbenes is first order in base and first order in reactant. The mechanism of this reaction is discussed in terms of the kinetic-acidity function correlation, the substituent effects, and the activation parameters. The reactions of 1,1-bis-(4-nitrophenyl)ethene and 4,4'-dinitrobenzophenone with hydroxide or alkoxide ions in DMSO are described. / Science, Faculty of / Chemistry, Department of / Graduate