Nonlinear Solution of the Time Eigenvalue of a Fast Burst Reactor Using the Finite Volume Method

This effort models fast burst reactors using the one dimensional, one group neutron diffusion equation to solve for the time eigenvalue, a method for which an analytical solution exists against which the numerical results can be verified. An existing solution method is enhanced by the addition of a second order accurate finite volume discretization, which is then used to model two separate fast burst reactors. The results of these models are then compared to the results of previous work, the analytical solution, and existing experimental burst width data for each of the two reactors

Observed Teleconnections in Northern Winter: Subseasonal Evolution and Tropical Linkages

Teleconnections refer to the climate variability links between non-contiguous geographic regions, and tend to be associated with variability in both space and time of the climate’s semi-permanent circulation features. Teleconnections are well-developed in Northern winter, when they influence subseasonal-to-seasonal climate variability, notably, in surface temperature and precipitation. This work is comprised of four independent studies that improve understanding of tropical-extratropical teleconnections and their surface climate responses, subseasonal teleconnection evolution, and the utility of teleconnections in attribution of extreme climate events. After an introduction to teleconnection analysis as well as the major teleconnection patterns and associated climatic footprints manifest during Northern winter, the lagged impact of the Madden-Julian Oscillation (MJO) on subseasonal climate variability is presented. It is found that monitoring of MJO-related velocity potential anomalies is sufficient to predict MJO impacts. These impacts include, for example, the development of significant positive temperature anomalies over the eastern United States one to three weeks following an anomalous convective dipole with enhanced (suppressed) convection centered over the Indian Ocean (western Pacific). Subseasonal teleconnection evolution is assessed with respect to the Pacific-North America (PNA) pattern and the North Atlantic Oscillation (NAO). This evolution is analyzed both in the presence and absence of MJO-related circulation anomalies. It is found that removal of the MJO results only in small shifts in the centers of action of the NAO and PNA, and that in either case there is a small but significant lag in which the NAO leads a PNA pattern of opposite phase. Barotropic vorticity analysis suggests that this relationship may result in part from excitation of Rossby waves by the NAO in the Asian waveguide. An attempt is made to elegantly differentiate between the MJO extratropical response and patterns of variability more internal to the extratropics. Analysis of upper-level streamfunction anomalies is successful in this regard, and it is suggested that this is the preferred method for the real time monitoring of tropical-extratropical teleconnections. The extreme 2013-2014 North American winter is reconstructed using teleconnection analysis, and it is found that the North Pacific Oscillation-West Pacific (NPO/WP) pattern was the leading contributor to climate anomalies over much of North America. Such attribution is cautionary given the propensity to implicate the tropics for all midlatitude climate anomalies based on the El Niño-Southern Oscillation (ENSO) paradigm. A recent hypothesis of such tropical influence is presented and challenged

Stronger at Depth: Jamming Grippers as Deep Sea Sampling Tools

In this work we experimentally demonstrate (a) that the holding strength of universal jamming grippers increases as a function of the jamming pressure to greater than three atmospheres, and (b) that jamming grippers can be used for deep sea grasping tasks in ambient pressures exceeding one hundred atmospheres, where such high jamming pressures can be readily achieved. Laboratory experiments in a pressurized, water filled test cell are used to measure the holding force of a \u27universal\u27 style jamming gripper as a function of the pressure difference between internal membrane pressure and ambient pressure. Experiments at sea are used to demonstrate that jamming grippers can be installed on, and operated from, remotely operated vehicles (ROVs) at depths in excess of 1200m. In both experiments, the jamming gripper consists of a latex balloon filled with a mixture of fresh water and ~200 micron glass beads, which are cheaply available in large quantities as sand blasting media. The use of a liquid, rather than gas, as the fluid media allows operation of the gripper with a closed loop fluid system; jamming pressure is controlled with an electrically driven water hydraulic cylinder in the lab, and with an oil hydraulic driven large-bore water hydraulic cylinder at sea

Differential roles of ERK-MAPKinase in WEHI-231 cell apoptosis and growth

BCR-ligation in B lymphocytes results in differential biological responses according to the maturational stage of the cell. Thus, while mature B lymphocytes become activated and proliferate in response to antigen receptor crosslinking, immature B lymphocytes become unresponsive or undergo apoptosis. Although these biological responses to antigen are well reported, the signalling pathways activated in each scenario are still poorly defined. In particular, the signalling cascades that result in the apoptosis of immature B lymphocytes which recognise self-antigen are still unclear. Recent studies within our group have highlighted the phospholipase, CPLA2, as a possible transducer of apoptotic signals following BCR-ligation (53) in WEHI-231 cells. Additionally, CD40 co-stimulation has been shown to rescue immature B lymphocyte from BCR-mediated apoptosis. We were therefore interested in investigating the signalling pathways linking the BCR to cPLA2 activation and the mechanisms utilised by CD40 co-stimulation in the reversal of BCR-mediated apoptosis. Initial studies examined the activation of the MAPKinase family of enzymes as these protein kinases, along with Ca2+, have been implicated in the activation of CPLA2. Our studies indicated that BCR-ligation induced the activation of a short, transient, ERK-MAPKinase signal, but not p38 MAPKinase or JNK. Additional studies have shown that inhibition of this ERK-MAPKinase signal by pharmacological means reduces BCR-induced apoptosis and cPLA2 activation. Interestingly, CD40 costimulation was shown to uncouple the BCR from ERK-MAPKinase activation, suggesting the prevention of cPLA2 activation may account for the anti-apoptotic properties of CD40 co-stimulation. BCR-induced apoptosis of WEHI-231 cells is known to occur approximately 24-48 hours post receptor ligation. We therefore examined the activity of ERK- MAPKinase over these time periods. Interestingly, untreated WEHI-231 cells were shown to exhibit a basal cycling, ERK-MAPKinase activity, suggesting this protein was involved in the normal proliferation of these cells. BCR-ligation was shown to abolish this signal after approximately 2-4hsuggesting that BCR-induced growth arrest involves the down-regulation of this cyclic ERK-MAPKinase activity. Additionally, CD40 co-stimulation was shown to restore this proliferative ERK-MAPKinase signal. Inhibitor studies corroborated this proposal that these late, cycling ERK-MAPKinase signals contribute to basal and CD40-rescued growth and proliferation of WEHI-231 cells. In summary, these results suggest differential roles for ERK-MAPKinase in regulating WEHI-231 cell fate. Firstly, an early, BCR-stimulated apoptotic signal, and secondly, a long-term proliferative signal. They also suggest that the induction of growth arrest and apoptosis in WEHI-231 cells result from the activation of distinct signalling pathways. We therefore investigated possible mechanisms involved in both the suppression, and re-establishment, of proliferative ERK-MAPKinase activity by BCR- ligation and CD40 co-stimulation respectively. Firstly, we examined the role of PI(3)K which is known to be involved in the induction of survival signals and ERK- MAPKinase activation in other cell systems. Our results suggested that PI(3)K mediated PtdIns(3,4,5)P3 generation does not play a role in CD40-mediated rescue from BCR-induced growth arrest. These results were corroborated by the inability to detect activity of the anti-apoptotic protein, Akt, following CD40 co-stimulation. Inhibitor studies did however indicate that PI(3)K activity plays a role in the basal proliferation of WEHI-231 cells. However, PtdIns(3,4,5)P3 generation, unlike basal ERK- MAPKinase, was not found to be cyclic in nature. These findings do not rule out a role for the involvement of other phosphatidylinositol species generated by PI(3)K activity, including PtdIns(3,4)P2 which is known to activate ERK-MAPKinase. (Abstract shortened by ProQuest.)

Analyzing mechanisms and microscopic reversibility of self-assembly

We use computer simulations to investigate self-assembly in a system of model chaperonin proteins, and in an Ising lattice gas. We discuss the mechanisms responsible for rapid and efficient assembly in these systems, and we use measurements of dynamical activity and assembly progress to compare their propensities for kinetic trapping. We use the analytic solution of a simple minimal model to illustrate the key features associated with such trapping, paying particular attention to the number of ways that particles can misbind. We discuss the relevance of our results for the design and control of self-assembly in general.Comment: 11 pages, 8 figures. Discussion clarified in response to referee coment

Pedestrian Solution of the Two-Dimensional Ising Model

The partition function of the two-dimensional Ising model with zero magnetic field on a square lattice with m x n sites wrapped on a torus is computed within the transfer matrix formalism in an explicit step-by-step approach inspired by Kaufman's work. However, working with two commuting representations of the complex rotation group SO(2n,C) helps us avoid a number of unnecessary complications. We find all eigenvalues of the transfer matrix and therefore the partition function in a straightforward way.Comment: 10 pages, 2 figures; eqs. (101) and (102) corrected, files for fig. 2 fixed, minor beautification

Synthesis of a Vocal Sound from the 3,000 year old Mummy, Nesyamun ‘True of Voice’

The sound of a 3,000 year old mummified individual has been accurately reproduced as a vowel-like sound based on measurements of the precise dimensions of his extant vocal tract following Computed Tomography (CT) scanning, enabling the creation of a 3-D printed vocal tract. By using the Vocal Tract Organ, which provides a user-controllable artificial larynx sound source, a vowel sound is synthesised which compares favourably with vowels of modern individuals

An exploratory factor analysis to measure self-efficacy in instrumental and vocal performance among university music students

The purpose of this study was to explore, validate and develop the Music Performance Self-Efficacy (MPSES) among University Music Students. The instrument of this study was adapted through the Micheal Zelanak study. A Total of 100 respondents from the Institute of Higher Learning in Malaysia were randomly selected in the data collection for this pilot study. Exploratory factor analysis was applied in the analysis of this study. To determine whether a particular item was significantly loaded, standard errors for factor loading were computed and utilized efficiently. This is to ascertain whether the difference between the factor loading of two or more items on the same factor is statistically significant. A total of 22 of the 24 items were categorized based on four dimensions, which are ‘Mastery Experiences’, ‘Vicarious Experiences' , ‘Verbal or Social Persuasion’ and ‘Psychological State’. The internal consistency value ranged from 0.78 to 0.91 while the overall reliability of the instrument was .92. The findings of this study indicate that the MPSES instrument was valid and reliable to measure self-efficacy among instrumental and vocal performance students at the university. Future study using a wide and varied of samples was recommended