Techniques which utilise a signal's Higher Order Statistics (HOS) can reveal information about non-Gaussian signals and nonlinearities which cannot be obtained using conventional (second-order) techniques. This information may be useful in speech processing because it may provide clues about how to construct new models of speech production which are better than existing models. There has been a recent surge of interest in the application of HOS techniques to speech processing, but this has been handicapped by a lack of understanding of what the HOS properties of speech signals are. Without this understanding the HOS information which is in speech signals can not be efficiently utilised. This thesis describes an investigation into the use of HOS techniques, in particular the third-order frequency domain measure called the bispectrum, to speech signals. Several issues relating to bispectral speech analysis are addressed, including nonlinearity detection, pitch-synchronous analysis, estimation criteria and stationarity. A flaw is identified in an existing algorithm for detecting quadratic nonlinearities, and a new detector is proposed which has better statistical properties. In addition, a new algorithm is developed for estimating the normalised bispectrum of signals contaminated by transient noise. Finally the tools developed in the study are applied to a specially constructed database of continuant speech sounds. The results are consistent with the hypothesis that speech signals do not exhibit quadratic nonlinearity.

In recent years, Digital subscriber line (DSL) technology has been gaining popularity as a high speed network access technology, capable of the delivery of multimedia services. A major impairment for DSL is impulse noise in the telephone line. However, evaluating the data errors caused by this noise is not trivial due to its complex statistical nature, which until recently had not been well understood, and the complicated error mitigation and framing techniques used in DSL systems. This thesis presents a novel analysis of the impact of impulse noise and the DSL framing parameters on transmission errors, building on a recently proposed impulse noise model. It focuses on errors at higher protocol layers, such as asynchronous transfer mode (ATM), in the most widely used DSL version, namely Asymmetric DSL (ADSL). The impulse noise is characterised statistically through its amplitudes, duration, inter-arrival times, and frequency spectrum, using the British Telecom / University of Edinburgh / Deutsche Telekom (BT/UE/DT) model. This model is broadband, considers both the time and the frequency domains, and accounts for the impulse clustering. It is based on recent measurements in two different telephone networks (the UK and Germany) and therefore is the most complete model available to date and suited for DSL analysis. A new statistical analysis of impulse noise spectra from DT measurements shows that impulse spectra can be modelled with three spectral components with similar bandwidth statistical distributions. Also, a novel distribution of the impulse powers is derived from the impulse amplitude statistics. The performance of a generic ADSL modem is investigated in an impulse noise and crosstalk environment for different bit rates and framing parameters. ATM cell and ADSL frame error rates, and subjective MPEG2 video quality are used as performance metrics. A new modification of a bit loading algorithm is developed to enable stable convergence of the algorithm with trellis coding and restricted subtone constellation size. It is shown that while interleaving brings improvement if set at its maximum depth, at intermediate depths it actually worsens the performance of all considered metrics in comparison with no interleaving. No such performance degradation is caused by combining several symbols in a forward error correction (FEC) codeword, but this burst error mitigation technique is only viable at low bit rates. Performance improvement can also be achieved by increasing the strength of FEC, especially if combined with interleaving. In contrast, trellis coding is ineffective against the long impulse noise error bursts. Alien as opposed to kindred crosstalk degrades the error rates and this is an important issue in an unbundled network environment. It is also argued that error free data units is a better performance measure from a user perspective than the commonly used error free seconds. The impact of impulse noise on the errors in DSL systems has also been considered analytically. A new Bernoulli-Weibull impulse noise model at symbol level is proposed and it is shown that other models which assume Gaussian distributed impulse amplitudes or Rayleigh distributed impulse powers give overly optimistic error estimates in DSL systems. A novel bivariate extension of the Weibull impulse amplitudes is introduced to enable the analysis of orthogonal signals. Since an exact closed-form expression for the symbol error probability of multi-carrierQAM assuming Bernoulli-Weibull noise model does not exist, this problem has been solved numerically. Multi-carrier QAM is shown to perform better at high signal-to-noise ratio (SNR), but worse at low SNR than single carrier QAM, in both cases because of the spreading of noise power between subcarriers. Analytical expressions for errors up to frame level in the specific case of ADSL are then derived from the impulse noise model, with good agreement with simulation results. The Bernoulli-Weibull model is applied to study the errors in single-pair highspeed DSL (SHDSL). The performance of ADSL is found to be better when the burst error mitigation techniques are used, but SHDSL has advantages if low bit error rate and low latency are required.

The introduction of cellular wireless systems in the 1980s has resulted in a continuous and growing demand for personal communication services. This demand has made larger capacity systems necessary. With the interest from both the research community and industry in wireless code-division multiple-access (CDMA) systems, the application of multiuser detection (MUD) techniques to wireless systems is becoming increasingly important. MUD is an important area of interest to help obtain the significant increase in capacity needed for future wireless services. The standardisation of direct-sequence CDMA (DS-CDMA) systems in the third generation of mobile communication systems has raised even more interest in exploiting the capabilities and capacity of this type of technology. However, the conventional DS-CDMA system has the major problem of multiple-access interference (MAI). The MAI is unavoidable because receivers deal with information which is transmitted not by a single source but by several uncoordinated and geographically separated sources. As a result, the capacity of these systems is inherently interference limited by other users. To overcome these limitations, MUD emerges as a promising approach to increase the system capacity. This thesis addresses the problem of improving the downlink capacity of a coded DS-CDMA system with the use of MUD techniques at the mobile terminal receiver. The optimum multiuser receiver scheme is far too computational intensive for practical use. Therefore, the aim of this thesis is to investigate sub-optimal multiuser receiver schemes that can exploit the advantages of MUD but also simplify its implementation. The attention is primarily focused on iterative MUD receiver schemes which apply the turbo multiuser detection principle. Essentially this principle consists of an iterative exchange of extrinsic information among the receiver modules to achieve improved performance. In this thesis, the implementation of an iterative receiver based on a linear MUD technique and a cancellation scheme over an additive white Gaussian noise (AWGN) channel is first proposed and analysed. The interference analysis shows that good performance is achieved using a lowcomplexity receiver structure. In more realistic mobile channels, however, this type of receiver suffers from the presence of higher levels of interference resulting in poor receiver performance. The reason for this is that in such scenarios the desired signals are no longer linearly separable. Therefore, non-linear detection techniques are required to provide better performance. With this purpose, a hybrid iterative multiuser receiver is investigated for the case of a stationary multipath channel. The incorporation of antenna arrays is an effective and practical technique to provide a significant capacity gain over conventional single-antenna systems. In this context, a novel space-time iterative multiuser receiver is proposed which achieves a large improvement in spectral efficiency and performance over multipath fading channels. In addition, it is shown that this architecture can be implemented without a prohibitive complexity cost. The exploitation of the iterative principle can be used to approach the capacity bounds of a coded DS-CDMA system. Using the Shannon’s sphere packing bound, a comparison is presented to illustrate how closely a practical system can approach the theoretical limits of system performance.

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Over 100 years after the Flexner Report first revolutionized medical education, medical schools across the United States are rethinking the role of scholarly research in their curricula. Scholarly research helps fulfill a number of essential elements of the medical school curriculum. The Scholarly Project (SP) engenders self‐directed independent learning, critical thinking skills, writing skills, life‐long learning, and many other objectives. The SP also allows students to assess evidence and the credibility of sources. According to a 2010 study, the Association of American Medical Colleges (AAMC) Curriculum Directory listed 84 medical schools with required research and 9 schools with a required thesis. This research requirement can take on many forms, some of which have been outlined for specific medical schools. Since then, more schools have embraced SP’s in their curricula, and the SP requirements and objectives have evolved dramatically at many U.S. medical schools. This project aims to (1) identify which U.S. allopathic medical schools have required and elective SP’s, (2) determine the components of these SP’s with respect to the duration and placement within the four‐year curriculum, the types of projects that qualify as SPs, the capstone requirement for the finished SP product, the curricular elements, and the objectives of the SP, and (3) determine how many schools have a required, four‐year longitudinal, hypothesis‐driven SP that culminate in a manuscript or thesis. The 136 allopathic medical schools on the AAMC Application Service website as of September 4, 2014 were included in this research. The individual website of each school was queried to attempt to determine the presence and characteristics of a formal SP within the curriculum. Each school was then contacted with the information that was found from the initial query in order to verify and/or elaborate on the preliminary results. Each SP was analyzed to determine (1) whether it was required or optional, (2) its duration and placement within the 4‐year curriculum, (3) the capstone requirement, (4) whether the research was required to be hypothesis‐driven, (5) the topic areas available for students, (6) whether there was formal curriculum in scholarly pursuit within the general medical curriculum, and (7) what the program objectives were. A total of 136 medical schools were surveyed in this study. Our analysis revealed that 78 of these schools include some structured SP in their curricula. Of these, 48 SPs are required, and 30 are optional. The majority of these SPs (36) require less than 1 year for completion. A total of 48 of the 78 medical schools had a manuscript or thesis requirement for the final capstone. Of the 48 schools with a required SP, 25 required the research to be hypothesis driven. A total of 43 of the 78 schools included required scholarship/research curricula as part of the overall medical education curriculum. The objectives of the programs are described in detail in this study. This study identified four medical schools with a required, 4‐year longitudinal, hypothesis‐driven SP that culminates with production of a manuscript or thesis. The four allopathic medical schools with a required, 4‐year longitudinal, hypothesisdriven SP that culminates in a manuscript/thesis are as follows: the Albert Einstein College of Medicine of Yeshiva University, the University of Arizona College of Medicine‐ Phoenix, the Virginia Tech Carilion School of Medicine and Research Institute, and Yale University. The details of each program are explored in the text.

My work focuses on my physical connection to the earth. I translate what I see and visualize in nature into graphic shapes and patterns using textiles, fibers, and paints. Further, I interweave these materials through a variety of techniques, and I incorporate sewn lines to create compositions highlighting natural elements that depict the course of life. I employ a hands-on, low technology approach. This tactic contrasts my work as a professional graphic designer. While my professional efforts generally lack a physical connection with nature, due to digital simulations of real objects, my personal artwork allows me to step away from the insipid technology tools commonly used in today’s society.

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