The Enhancement of Interfacial Exciton Dissociation by Energetic Disorder is a Nonequilibrium Effect

The dissociation of excited electron-hole pairs is a microscopic process that is fundamental to the performance of photovoltaic systems. For this process to be successful, the oppositely charged electron and hole must overcome an electrostatic binding energy before they undergo ground state recombination. Here we use a simple model of charge dynamics to investigate the role of molecular disorder in this process. This model reveals that moderate spatial variations in electronic energy levels, such as those that arise in disordered molecular systems, can actually increase charge dissociation yields. We demonstrate that this is a nonequilibrium effect that is mediated by the dissipation driven formation of partially dissociated intermediate states that are long-lived because they cannot easily recombine. We present a kinetic model that incorporates these states and show that it is capable of reproducing similar behavior when it is parameterized with nonequilibrium rates.Comment: 25 pages, 7 figure

Experimental and theoretical investigation of the behaviour of brickwork cladding panel subjected to lateral loading

This thesis deals mainly with the resistance of single leaf brickwork cladding panels subjected to uniform lateral pressure. Such panels when supported on three or four sides bend like thin plates and are subjected to bi-axial bending. A bi-axial failure criterion for brickwork, which shows both strength and stiffness orthotropies, is required to predict the strength of the cladding panels. A systematic investigation was undertaken to establish the failure criterion of brickwork in bi-axial bending using a novel test method. A total number of 33 cross-beams in which both vertical and horizontal moments can be applied simultaneously was tested to define the failure criterion. From the tests, it appears that the strength in the weaker direction is enhanced in biaxial bending. In most cases, the load was shed from the weaker to the stronger direction after cracking. Once the section cracks, it is not capable of carrying any moment, which indicates the brittle nature of masonry. A conventional plate bending finite element program was modified incorporating the bi-axial failure criterion which takes into account the load-shedding observed in the tests. A smeared crack modelling technique was used to model the progressive cracking in bi-axial bending. Once the material properties in bi-axial bending were established and numerical modelling was carried out to predict the behaviour, it was essential to apply the theoretical model to walls subjected to lateral loading. A total number of 15 walls with different aspect ratios and boundary conditions was tested for comparison with the numerical method. Good agreement was obtained between the theoretical model and experimental results. All walls were tested under ideal boundary conditions so that rotational restraint at the supports could be avoided. Similar observations of load shedding from the weaker vertical direction to the stronger horizontal direction were observed also in the wall tests. This was confirmed by measuring the drop and increase in the reactions in the weaker and stronger directions. This was also confirmed from strain measurements in two orthogonal directions before and after cracking. These results also indicate without doubt that a cracked section cannot support any moment. This modified finite element program using the bi-axial failure criterion developed in this thesis was also used to compare the results with the wall test carried out by other researchers. A good agreement between the theoretical and the experimental results of wall with and without openings and subjected to lateral loading was also obtained. Hence, this finite element program using the bi-axial failure criterion can be used for the design of laterally loaded brickwork panels with confidence

Exploring the physical health of young people with first-episode psychosis

First-episode psychosis affects young people’s mental and physical capacity to function optimally. In addition, the use of antipsychotic medications to treat psychosis can increase an individual’s risk of developing metabolic syndrome which may lead to serious physical health problems. This research used a mixed methods approach to investigate the impact of psychosis and its treatment on young people’s health and then make recommendations to improve the physical health care for this cohort

Numerical Approximation to the Inverse Function of the Cumulative Chi-Square, t, and F Distribution

In the past, tables have been published for the chi­-square, t and F distributions. These tables have their own limitations with respect to the number of percentage points and degrees of freedom that are applicable. For instance, most tables for the chi-square distribution list tabular chi-square value for probabilities, .995, .99, .975, .95, .75, .5, .25, .1, .05, .025, .01, .005, .001, .0005, .0001 with degrees of freedom (1, 30, 1) and (40, 120, 10). How­ever, suppose we want to know the chi-square value for probability .96 with degrees of freedom 10, or probability .95 with degrees of freedom 35; we would find other tables incomplete at this point. Besides, as the computer is get­ting widely used in research, it is worthwhile to have computer programs written to generate some of statistical functions rather than strictly to be limited by the tables. Consequently, there have been methods developed to approximate chi-square, t and F value, when degrees of freedom and probability are known. It is the purpose of this study to present the methods of each individual dis­tribution and evaluate its accuracy. Thus, the scope of this paper includes the following: 1. The definition and inverse function of each dis­tribution. 2. The numerical approximate methods and examples. 3. A computer Fortran IV program to maximize the accuracy of calculation. 4. A comparison of the results obtained by numerical approximation with the known tabular value. 5. An evaluation of the capacity of these numerical methods

Haemostatic status in patients with ovarian cancer compared with patients with benign ovarian cysts and the study of the relationships between haemostatic levels in ovarian cancer patients with known survival outcome

Ph.DDOCTOR OF PHILOSOPH

DEVELOPMENT OF TOXICITY MODEL

Inherent safety has been recognized as a design approach useful to remove or reduce hazards at the source instead of controlling them with add-on protective barriers. Methods developed to date have largely been for the evaluating the safety of a proposed design. At the moment it seems that the best practice is not adopted quickly enough by the potential practitioners. The aim ofthis project is to develop a toxicity model that can be used in the design stages of chemical producing plants to predict the concentration at a given distance away from the point of release. The scope ofthis project is to create a toxicity model for ammonia. The model consists of two major parts, which are Gaussian Plume Equation and toxicity of ammonia. The information on these two parts need to be merged so user(s) can then find out the severity of the concentration of ammonia at a given distance away from the point of incident. Using Microsoft Excel as the program to run this toxicity model, the interface is arranged to make it as user-friendly as possible. Some of the important parameters to be keyed into the model are molecular weight, density, temperature, pressure, flow rate and distance of leak/rupture from ground level. Overall, this project can be used to evaluate whether it is feasible for a chemical producing plant to be built near housing areas. Further improvements are necessary to commercialize and integrate this project with other riskeffects estimation

Query-Efficient Locally Decodable Codes of Subexponential Length

We develop the algebraic theory behind the constructions of Yekhanin (2008) and Efremenko (2009), in an attempt to understand the ``algebraic niceness'' phenomenon in $\mathbb{Z}_m$. We show that every integer $m = pq = 2^t -1$, where $p$, $q$ and $t$ are prime, possesses the same good algebraic property as $m=511$ that allows savings in query complexity. We identify 50 numbers of this form by computer search, which together with 511, are then applied to gain improvements on query complexity via Itoh and Suzuki's composition method. More precisely, we construct a $3^{\lceil r/2\rceil}$-query LDC for every positive integer $r<104$ and a $\left\lfloor (3/4)^{51}\cdot 2^{r}\right\rfloor$-query LDC for every integer $r\geq 104$, both of length $N_{r}$, improving the $2^r$ queries used by Efremenko (2009) and $3\cdot 2^{r-2}$ queries used by Itoh and Suzuki (2010). We also obtain new efficient private information retrieval (PIR) schemes from the new query-efficient LDCs.Comment: to appear in Computational Complexit