Predicting and identifying signs of criticality near neuronal phase transition

This thesis examines the critical transitions between distinct neural states associated with the transition to neuron spiking and with the induction of anaesthesia. First, mathematical and electronic models of a single spiking neuron are investigated, focusing on stochastic subthreshold dynamics on close approach to spiking and to depolarisation-blocked quiescence (spiking death) transition points. Theoretical analysis of subthreshold neural behaviour then shifts to the anaesthetic-induced phase transition into unconsciousness using a mean-field model for interacting populations of excitatory and inhibitory neurons. The anaesthetic-induced changes are validated experimentally using published electrophysiological data recorded in anaesthetised rats. The criticality hypothesis associated with brain state change is examined using neuronal avalanches for experimentally recorded rat local field potential (LFP) data and mean-field pseudoLFP simulation data. We compare three different implementations of the FitzHugh--Nagumo single spiking neuron model: a mathematical model by H. R. Wilson, an alternative due to Keener and Sneyd, and an op-amp based nonlinear oscillator circuit. Although all three models can produce nonlinear ``spiking" oscillations, our focus is on the altering characteristics of noise-induced fluctuations near spiking onset and death via Hopf bifurcation. We introduce small-amplitude white noise to enable a linearised stochastic analyses using Ornstein--Uhlenbeck theory to predict variance, power spectrum and correlation of voltage fluctuations during close approach to the critical point, identified as the point at which the real part of the dominant eigenvalue becomes zero. We validate the theoretical predictions with numerical simulations and show that the fluctuations exhibit critical slowing down divergences when approaching the critical point: power-law increases in the variance of the fluctuations simultaneous with prolongation of the system response. We expand the study of stochastic behaviour to two spatial dimensions using the Waikato mean-field model operating near phase transition points controlled by the infusion or elimination of anaesthetic inhibition. Specifically, we investigate close approach to the critical point (CP), and to the points of loss of consciousness (LOC) and recovery of consciousness (ROC). We select the equilibrium states using $\lambda$ anaesthetic inhibition and $\Delta V^{\text{rest}}_e$ cortical excitation as control parameters, then analyse the voltage fluctuations evoked by small-amplitude spatiotemporal white noise. We predict the variance and power spectrum of voltage fluctuations near the marginally stable LOC and ROC transition points, then validate via numerical simulation. The results demonstrate a marked increase in voltage fluctuations and spectral power near transition points. This increased susceptibility to low-intensity white noise stimulation provides an early warning of impending phase transition. Effects of anaesthetic agents on cortical activity are reflected in local field potentials (LFPs) by the variation of amplitude and frequency in voltage fluctuations. To explore these changes, we investigate LFPs acquired from published electrophysiological experiments of anaesthetised rats to extract amplitude distribution, variance and time-correlation statistics. The analysis is broadened by applying detrended fluctuation analysis (DFA) to detect long-range dependencies in the time-series, and we compare DFA results with power spectral density (PSD). We find that the DFA exponent increases with anaesthetic concentration, but is always close to 1. The penultimate chapter investigates the evidence of criticality in anaesthetic induced phase-transitions using avalanche analysis. Rat LFP data reveal an avalanche power-law exponent close to $\alpha = 1.5$, but this value depends on both the time-bin width chosen to separate the events and the \textit{z}-score threshold used to detect these events. Power-law behaviour is only evident at lower anaesthetic concentrations; at higher concentrations the avalanche size distribution fails to align with a power-law nature. Criticality behaviour is also indicated in the Waikato mean-field model for anaesthetic-induced phase-transition using avalanches detected from the pseudoLFP time-series, but only at the critical point (CP) and at the secondary phase-transition points of LOC and ROC. In summary, this thesis unveils evidence of characteristic changes near phase transition points using computer-based mathematical modelling and electrophysiological data analysis. We find that noise-driven fluctuations become larger and persist for longer as the critical point is closely approached, with similar properties being seen not only in single-neuron and neural population models, but also in biological LFP signals. These results consistent with an increase of susceptibility to noise perturbations near phase transition point. Identification of neuronal avalanches in rat LFP data for low anaesthetic concentrations provides further support for the criticality hypothesis

Urban Heat Island and Household Energy Consumption in Bangkok, Thailand

AbstractThis study focuses on the urban heat island (UHI) development and its impact on household energy consumption. Hourly air temperature data were used to study the characteristics and intensities of UHI in Bangkok area. A survey questionnaire of 400 randomly selected respondents is conducted to explain the relationship between UHI intensity and household energy consumption. Cooling Degree Days (CDD) index was used to establish the correlation between UHI and energy consumption. The result indicates that the presence of UHI in Bangkok plays a significant role in residential energy use, directly and indirectly. UHI is found to have association with the air conditioning equipment in Bangkok and increase the monthly electricity bill. Energy consumption is found to have positive association with CDD, which implies that UHI have significant influence on the household energy consumption. The study concludes that combining the concept of UHI mitigation and adaptation planning and energy-efficient housing design will contribute to better solutions for creating a more energy-efficient city

The Spatial Distribution Of Cn Radicals In The Coma Of Comet Encke

Comets are important for solar system studies because their interiors hold evidence of the conditions in which they formed in the outer solar system. However, the coma obscures the nucleus from view when observations are most easily performed, thus it is important to understand the nature of cometary comae. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Observations of CN were obtained from October 22-24, 2003, using the 2.7 m Cassegrain telescope at McDonald Observatory in Fort Davis, TX. The classical vectorial model was modified by introducing a fan-like feature in order to explain Encke’s aspherical coma. The results are consistent with HCN being the photodissociative parent of CN, based on the OH/CN ratios and the physical parameters used to match the model profiles with the observations

GPS usage and infrastructure needs for machine guidance and control in the construction projects associated with QDMR

[Abstract]: This dissertation analyzed the GPS usage and infrastructure needs for machine guidance and control, in the construction projects associated with QDMR, in order to provide recommendations for future infrastructure needs. Research studies have confirmed that, GPS usage on machine guidance and control in the construction industry, within a VRS CORS environment increase the productivity of the projects. Investigation about the GPS usage on machine guidance and control, for construction projects, associated with QDMR was selected, as the limit of this study, in order to make recommendations for future infrastructure needs, with respect to a possible VRS expansion. Three main research approaches were designed in the project, and the results were further investigated. Geographical locations, spread and density, budget allocations and the durations of the projects were analyzed, to find out a clear suite of evidence, to prove the argument. The business case and the associated cost /benefit analysis, confirmed that, it is beneficial to expand VRS coverage to allow QDMR, to use machine guidance and control on construction projects in south east Queensland. Results not only demonstrated that, the VRS expansion is possible in the south east region, but also, suggested that multiple strategies should be adopted, when establishing GPS infrastructure in Queensland, as a whole. VRS expansion is suitable for the locations, with high density of construction projects, while other districts may provide with either, independent GPS networks or should still use, stand alone systems. Recommendations on future GPS infrastructure developments in Queensland based on the above findings and further possible research avenues were also included in this dissertation. Recommendations on future GPS infrastructure developments have been prepared for the first time in Queensland, from a research study, considering a situation applied to a major government organization in Queensland. These recommendations may be used by DNRW, QDMR and other potential GPS users, to develop strategies, for designing future GPS infrastructure in Queensland, at government level

Extract Of Gelidiella Acerosa (S-Act-1) As A Capacitation Agent For In Vitro Fertilisation In Goat

A study was conducted to determine if goat ovaries obtained from a slaughterhouse could be used for in vitro fertilisation (lVF). Three experiments were conducted to ascertain if a substance named S-ACT-l, extracted from a marine algae, (Gelidiella acerosa), with a chemical structure similar to heparin could be used for sperm capacitation. The acrosome reaction was tested by a dual staining technique (Experiment 1 ) and the zona free hamster penetration test (Experiment 2). In vitro maturation o f goat oocytes and fertilisation were assessed by the number of zygotes cleaving beyond the 2-cell stage (Experiment 3). Freshly ejaculated semen from two fertile bucks were used for sperm capacitation using two defined media (DM-H and DM-Ca). Heparin and S-ACT-l were tested at concentrations of 10, 20, 50 and 100 ug/ml. After incubating for 15 min. at 39° C with 5 % CO2 in air under maximum humidity, samples were stained with trypan blue and Giemsa stain (dual stain). The results indicated that the sperm treated with heparin and S-ACT - 1 showed similar staining characteristics

The Spatial Distribution Of OH And CN Radicals In The Coma Of Comet Encke

Multiple potential parent species have been proposed to explain CN abundances in comet comae, but the parent has not been definitively identified for all comets. This study examines the spatial distribution of CN radicals in the coma of comet Encke and determines the likelihood that CN is a photodissociative daughter of HCN in the coma. Comet Encke is the shortest orbital period (3.3 years) comet known and also has a low dust-to-gas ratio based on optical observations. Observations of CN were obtained from 2003 October 22 to 24, using the 2.7 m telescope at McDonald Observatory. To determine the parent of CN, the classical vectorial model was modified by using a cone shape in order to reproduce Encke's highly aspherical and asymmetric coma. To test the robustness of the modified model, the spatial distribution of OH was also modeled. This also allowed us to obtain CN/OH ratios in the coma. Overall, we find the CN/OH ratio to be 0.009 +/- 0.004. The results are consistent with HCN being the photodissociative parent of CN, but we cannot completely rule out other possible parents such as CH(3)CN and HC(3)N. We also found that the fan-like feature spans similar to 90 degrees, consistent with the results of Woodney et al..NASAOffice of the Vice President for Research and Economic Development at Mississippi State UniversityMcDonald Observator

Analysis of Driving Skills based on Deep Learning using Stacked Autoencoders

Due to the advancement of automobile technology and increasing consumers demands, it is expected that automatic driving vehicles and manual driving vehicles will coexist in future automobile society. There are a number of people who are interested in driving and, they may think that the automatic driving vehicles are unnecessary. However, if the vehicle is operated manually, there is a possibility for driving skills of a driver to fluctuate due to drowsiness and fatigue and that may lead to accidents. In such a situation, it is important for vehicle to monitor the driver's driving conditions and provide with a driving support system or automatic driving options. In this research, we propose a method to classify driving skills of an individual driver with high precision based on deep learning (stacked autoencoders). In the experiments, driver’s driving skills were classified by combining sensor signals of curve driving data acquired from a driving simulator. As a result, a maximum driving skill recognition rate of 98.1% was achieved. In addition, the recognition rate was improved compared to the previous researches