The objective of the research is to achieve a systematic combination of acoustic echo reduction components that together achieve a robust performance of the MCAEC system as a whole. Conventional approaches to the acoustic echo reduction system typically assume that individual components would perform ideally. For example, the adaptive algorithm for AEC is often developed in the absence of strong near-end signal, the algorithm for RES is often an added module that is developed as a separate noise reduction component, and the decorrelation procedure for MCAEC is yet another add-on module that simply introduces some form of distortion to the reference signal. The main challenge is in designing a consistent criterion across all modules that can be jointly optimized to form a more consistent framework for acoustic echo reduction. The decorrelation procedure can potentially benefit from the system approach as well if it is designed by taking the near-end listener into account. The MCAEC system should be optimized not only for the echo cancellation and suppression performance, but also for the reference signal quality after the added distortion from the decorrelation procedure. Finally, a tuning strategy is presented to jointly optimize the parameters across all modules using object criteria.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper describes a kind of Microwave Digital Frequency Synthesizer used for S-band telemetry receivers. As well known many modern electronic systems employ a Frequency Synthesizer whose spectral purity is critical. The characteristics of a PLL (Phase-Locked Loop) Frequency Synthesizer, such as frequency resolution, phase noise, spurious suppression and switch time, should be compromised in our design. A heterodyne Frequency Synthesis is often considered as a good approach to solve the problem. But it is complicated in structure and circuit. A variable-reference-driven PLL Frequency Synthesizer was introduced which can give an improved trade-off among frequency resolution, phase noise, spurious suppression. In this paper the phase noise and spurious suppression characteristic of variable-reference-driven PLL Frequency Synthesizer is analyzed theoretically and compared with that of the heterodyne Frequency Synthesizer. For engineering application, a practical Microwave Digital Frequency Synthesizer used for telemetry receiver has been designed, which is characterized by simply structure, low phase noise and low spurious output. The output spectrum of experimental measurements is given.

Small cell lung cancer (SCLC) is characterised by rapid growth, early metastatic spread and poor long-term survival. The tumour is initially sensitive to chemotherapy and thus objective response rates are high. Unfortunately, this response is often short-lived and SCLC recurs with acquired drug resistance, resulting in early patient death. Despite intensive chemo- and radiotherapy regimes survival has not improved significantly in 20 years. Prior research suggests a critical role for the tumour microenvironment in the pathogenesis of other cancers. Therefore, investigating interactions between SCLC cells and components of the tumour stroma may identify novel therapeutic targets. This thesis demonstrates that extracellular matrix (ECM) proteins present in the tumour microenvironment protect SCLC cells in vitro from chemo- and radiotherapy induced cell cycle arrest and apoptosis via cell surface β1 integrins. Pharmacological and genetic inhibition of phosphoinositol-3 kinase signalling abrogates this effect, defining a central role for this pathway in SCLC de novo drug resistance. Furthermore, the protective effect of ECM occurs without alteration in chemotherapy-induced DNA damage allowing SCLC cells to survive with new genetic defects. Integrin-mediated drug resistance has been shown to be important in other tumours and thus development of strategies to inhibit this pathway may yield new anti-cancer treatments. The design of targeted agents to down-regulate integrin-ECM interaction requires an in depth understanding of the intracellular signals that modulate integrin affinity. Two such pathways are investigated in this thesis. 1) H-Ras, a dominant suppressor of integrin affinity, acts in part through phosphorylation of Erk. Data presented here demonstrate that H-Ras also suppresses integrins through a phospholipase-C epsilon (PLCε)-dependent pathway, thus explaining discrepancies in prior data and confirming a physiological role for this recently identified phospholipase. 2) The Notch signalling pathway has been shown to have important roles in both development and cancer. It is shown here that activation of Notch signalling increases β1 integrin affinity and can protect SCLC cells from chemotherapyinduced apoptosis. However the mechanisms appear to be different; Notch-1 modulates integrin activation through the small GTPase R-Ras and Notch-2 promotes SCLC cell survival. These results define a new Notch pathway, a novel integrin modulator and a potential therapeutic target in SCLC cells. In addition to ECM proteins, the tumour microenvironment contains immune cells that may contribute to cancer growth. The cellular composition of the SCLC stroma is poorly understood. The data presented here indicate that the microenvironment of SCLC is infiltrated by lymphocytes and macrophages, the degree of which independently predicts patient survival. This suggests that the host immune system may be able to suppress SCLC growth. It is well recognised that patients with SCLC have defects in cellular immunity which correlate with survival. An in vitro coculture model was used to investigate the underpinning mechanisms, showing SCLC cells can suppress CD4+ T-cell proliferation and macrophage CD86 expression. Furthermore, preliminary data suggest a role for a soluble factor released by SCLC cells that up-regulates CD4+ T-cell production of IL-10. The work in this thesis implies a complex interaction between SCLC cells, ECM and immune cells in the tumour microenvironment. Manipulation of these pathways may have important therapeutic implications. Further investigation is required to understand the mechanisms of this interplay, which may in part be aided by prospective analysis of patient tumour samples and an in vivo model of SCLC.

In the past decade, considerable attention has been paid to examination of the impact of amblyopia, and strabismus, upon the lives of the individuals. Although an extensive amount of literature exists regarding amblyopia and its associated visual defects, little is known about the contribution of the amblyopic eye in the habitual viewing condition (i.e. both eyes viewing). The purpose of these studies was to determine whether amblyopes are disadvantaged in the performance of tasks under habitual viewing conditions, highlighting any functional differences which may exist as a consequence of amblyopia. Secondly, the work aimed to investigate whether the amblyopic eye contributes to the habitual performance of these tasks. A simple light detection task, in a dichoptic arrangement based upon blue/yellow stimuli viewed through yellow filters, was used to investigate the above two aims and investigate the degree of interocular suppression in amblyopic participants. Using a 3D motion analysis system performance was assessed for an obstacle crossing task (adaptive gait) and a task of reaching for and grasping of an isolated object and in a 'cluttered' environment. Fine motor skills were assessed in a threading a needle task. On the whole it was found that amblyopes are not disadvantaged under habitual viewing conditions, and in cases where differences were found to exist this appeared to be in tasks requiring speed and accuracy. Consistently across all studies it was found that the amblyopic eye contributed in a positive manner, thus, as in visual normals, two eyes are better than one.

The effects of auditory efferent activity on peripheral physiology may be examined by presenting broadband noise (BBN) to the contralateral ear during otoacoustic emission (OAE) recordings. The presentation of BBN typically produces a reduction of OAE amplitudes in comparison to a condition without BBN. This is termed contralateral suppression. Limited information exists regarding the effects of contralateral BBN on responses observed at higher levels in the auditory system. The present study employed this paradigm to investigate interactions of attention and laterality on the transient evoked otoacoustic emission (TEOAE), auditory brainstem response (ABR) and cortical auditory evoked potentials (CAEP) P1-N1-P2. TEOAEs were evoked by 60 dB SPL clicks; ABRs and CAEPs were evoked by 60 dB SPL 2.0 kHz tone pips in 15 normally hearing adults. Four conditions were employed for each ear: 1) quiet (no noise); 2) 60 dB SPL contralateral BBN; 3) words (at -3 dB SNR) embedded in 60 dB SPL contralateral BBN while subjects classified words as animal versus food items; 4) words from condition #3 played backwards and embedded in 60 dB SPL contralateral BBN. For TEOAEs: 1) more suppression was evident in the active attention condition than the passive listening conditions and 2) right ear OAE amplitudes for the 8-18 ms time period exhibited more suppression in the presence of BBN for all noise conditions, although this did not meet statistical significance. For the ABR experiment, amplitudes in the noise conditions decreased in all epochs for the right ear, but not for the left. For the CAEP experiment, asymmetries were evident in temporal regions and an effect of contralateral noise was evident. The outcome of this investigation suggests that efferent activation by noise and active attention has diverse modulatory effects on electroacoustic and electrophysiologic responses along the auditory pathway.

No description available.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The objective of this research is to develop a wearable device that could harvest waste mechanical energy of the human hand movement and utilize this energy to suppress wrist tremors. Piezoelectric material is used to measure the hand movement signals, and the signal of wrist tremor is filtered to be utilized to suppress the tremor. In order to conduct the experiment of energy harvesting and tremor suppression, an experimental rig was fabricated. Two types of piezoelectric materials, PVDF (polyvinylidene fluoride) films and MFC (macro fiber composite) films, are used to harvest mechanical energy and used as actuators to suppress hand tremors. However, due to some shortages of the materials, these two types of materials are not used as actuators to suppress the wrist tremors. Thus, we use Matlab Simulink to simulate the tremor suppression with AVC (active vibration control) algorithm.

Introduction: In gymnastics, athletes perform twisting and flipping skills at high angular velocities. These athletes rely heavily on sensory information from the visual, proprioceptive, and vestibular systems. The vestibulo-ocular reflex (VOR) is responsible for stabilizing the visual field on the retina during head movement. To accomplish this, the eyes are reflexively moved in a direction opposite the head. In a twisting gymnast, this actually reduces the ability of gymnasts to see the landing during airborne skills. Hence it becomes necessary for the gymnasts to cancel or suppress their VOR in order to view the landing. Objective: The purpose of this research is to investigate the relationship between gymnastics skill level and their ability to suppress the VOR. Methods: Ten female gymnasts (mean age 15±2.2) were obtained via a sample of convenience from a local club. The sample included both competitive and recreational gymnasts. Subjects were asked to wear a measurement system that could track head and eye movements as they performed a series of visual tasks. Three experiments were performed: (1) a saccadic experiment – two horizontally fixed LEDs (±10°) were alternately lit in a non-predictable pattern to provide visual cues, (2) a VOR experiment – the subject was asked to perform yawl head movements to an audible metronome beat 11 while visually fixating on an LED target 1m away, and (3) a vestibulo-ocular reflex suppression/cancellation (VORc) experiment – a laser pointer was fixed to the subject‟s helmet close to the cyclopean eye (slaving the target to the head movement) and the subject was again asked to perform head movements to a metronome while visually fixating on the target. In both VOR experiments, the metronome frequency varied from 72 to 196 beats per minute. Eye and head position data were synchronously sampled at 250 and 100Hz respectively. Data were post-processed using MATLAB. Periodic calibrations were performed throughout the experiment to test the continued reliability of the data. Results: Saccadic peak velocities and latencies were calculated for the sample population. Their performance did not differ from the normal population. VOR and VORc gains were also calculated and compared. The higher level (competitive) gymnasts were better at suppressing their VOR. In addition, left/right VOR gain asymmetries correlated highly with twist direction in seven of the competitive gymnasts. Discussion/Conclusions: There is a correlation between VOR performance and gymnastic level. These results do not suggest that VOR differences develop as a result of practice. These differences may simply allow some individuals to become better performers. A longitudinal study on a larger population would be required to test the causal relationship between these variables.

Understanding mast cell development is central to allergic disease pathophysiology. Our laboratory has previously shown that cytokines such as IL-4 and IL-10 inhibit mast cell development from bone marrow progenitors. These studies encouraged our interest in other regulatory cytokines, including transforming growth factor β1 (TGF- β1). TGF- β1 has many cellular sources, one of which is CD4+CD25 regulatory T cells (Tregs). We wanted to determine the effects of Transforming Growth Factor (TGF) βl on mast cell development. We find that TGFβl decreased FcεRI, c-Kit, T1/ST2 and FcεR expression, and inhibited granule formation in developing mast cells. Accessory cells were not required for this inhibition. Smad3-deficiency did not alter the response of bone marrow cells to TGFβ1. TGFβl inhibited expression of the FcεRI a subunit protein, without decreasing β or γ proteins. Mast cells derived in the presence of TGFβl were functionally impaired, as IgE-mediated cytokine secretion was greatly reduced. The changes in granule formation and surface antigen expression were long-standing, as they were not reversed by transfer to W/WV mice. The TGF-β1 dependent transcriptional regulation of bone marrow cells from which mast cells develop was examined through DNA microarray analysis. Wild type (WT) bone marrow cells were stimulated with IL-3+SCF+vehicle or IL-3+SCF+TGF-βI for 10 days and their transcriptomes* analyzed. The results identified which components of transcriptional regulation were regulated by TGF- β1. Of particular interest was the upregulation of the β subunit of the FcεRI, inspite of no receptor surface expression and the differential regulation of various mast cell proteases (MCPs). This initial survey provides a potential starting point for further analysis of the role of TGF-β1 -dependent signaling in developing mast cells. Because they produce TGF-β1 and/or IL-10, regulatory T cell-dependent murine mast cell inhibition was examined. Co-culture of mast cells with regulatory T cells for 6 days downregulated mast cell number, high affinity IgE receptor and c-Kit surface expression. This led to a decrease in TNFa release making mast cells functionally impaired. By using Tregs from IL-10 KO mice, this effect was proven to be IL-10 dependent. Mast cells are mediators of inflammatory disease. TGFβl and IL-10 may contribute to mast cell homeostasis by inhibiting maturation from bone marrow precursors. The effects of TGFβ1 and regulatory T cell derived IL-10 result in greatly diminished expression of cell surface markers, reduced granulation, and lack of responsiveness to IgE-mediated activation. Thus TGFβl and/or CD+CD25+ T cells can serve as potent and multifunctional regulators of mast cell maturation and/or function.* A set of genes that are expressed in a cell at any given time.