Transglutaminase II (TG2) is a complex protein with five different reported activities. Increases in TG2 expression and TGase activity have previously been observed during wound healing in rat studies; however, it has been unclear whether these phenomena were directly involved in the healing process or if they were simply a by-product of it. The aims of this thesis were, thus, to determine if TG2 plays a role in wound healing in vivo and to elucidate the mechanism of any effects TG2 may have at the cellular level. TG2 ablation resulted in delayed wound healing. To gain mechanistic insight into this abnormality, primary fibroblast cultures from TG2-knockout and wildtype mouse embryos were analysed. TG2-null fibroblasts displayed decreased adhesion and integrin signalling during initial stages of adhesion. Intriguingly, TG2-null cells showed faster activation of Rac1 and RhoA in response to adhesion. Long-term adhesion of TG2-null fibroblasts resulted in increased basal phosphorylation of FAK and number of paxillin-stained focal adhesions, enhanced PI3-kinase signalling, faster actin dynamics and altered activation of p44/42 MAPK. These results are indicative of futile cycling of intracellular signalling pathways resulting from reduced focal adhesion turnover in the TG2-knockout fibroblasts. Rescue experiments demonstrated that TG2-mediated effects on cell adhesion occurred in the extracellular environment and that neither GTP-binding nor TGase activity is required for these effects. Results further showed that a ???compact??? conformation of TG2 was not required for this role of TG2. Interestingly, addition of recombinant TG2 to the extracellular environment increased cell spreading of TG2-null cells to a level far greater than that seen in wildtype cells, which did not increase their spreading in response to exogenous TG2. Demonstration of faster activation of the small GTPases in the TG2-null MEFs, and the apparent inhibition of exogenous TG2???s extracellular effects on cell spreading by endogenous protein in the wildtype cells, provide tantalising evidence for a role for intracellular TG2 in regulating activation of the small GTPases to promote efficient fibroblast migration. This work identifies TG2 as a facilitator of efficient wound closure through extracellular effects on integrin-mediated signalling and intracellular effects on activation of the small GTPases.

No description available.

The objective of the proposed research is to devise high-performance and low-complexity signal-detection algorithms for communication systems over fading channels. They include channel equalization to combat intersymbol interference (ISI) and multiple input multiple output (MIMO) signal detection to deal with multiple access interference (MAI) from other transmit antennas. As the demand for higher data-rate and more efficiency wireless communications increases, signal detection becomes more challenging. We propose novel transmission and iterative signal-detection techniques based on energy spreading transform (EST). Different from the existing iterative methods based on the turbo principle, the proposed schemes are independent of channel coding. EST is an orthonormal that spreads a symbol energy over the symbol block in time and frequency for channel equalization; space and time for MIMO signal detection with flat fading channels; and space, time, and frequency for MIMO signal detection with frequency-selective fading channels. Due to the spreading, EST obtains diversity in the available domains for the specific application and increases the reliability of the feedback signal. Moreover, it enables iterative signal detection that has near interference-free performance only at the complexity of linear detectors. Either a hard or soft decision can be fed back to the interference-cancellation stage at the subsequent iteration. The soft-decision scheme prevents error propagation of the hard-decision scheme for a low SNR and improves the performance. We analyze the performance of the proposed techniques. Analytical and simulation results show that these schemes perform very close to the interference-free systems.

No description available.

In a multiuser DS-CDMA system with frequency selectivity, each user’s spreading sequence is transmitted through a different channel and the autocorrelation and the cross correlation properties of the received sequences will not be the same as that of the transmitted sequences. The best way of designing spreading sequences for frequency selective channels is to design them at the receiver exploiting the users’ channel characteristics. By doing so, we can show that the designed sequences outperform single user AWGN performance. In existing sequence design algorithms for frequency selective channels, the design is done in the time domain and the connection to frequency domain properties is not established. We approach the design of spreading sequences based on their frequency domain characteristics. Based on the frequency domain characteristics of the spreading sequences with unconstrained amplitudes and phases, we propose a reduced-rank sequence design algorithm that reduces the computational complexity, feedback bandwidth and improves the performance of some existing sequence design algorithms proposed for frequency selective channels. We propose several different approaches to design the spreading sequences with constrained amplitudes and phases for frequency selective channels. First, we use the frequency domain characteristics of the unconstrained spreading sequences to find a set of constrained amplitude sequences for a given set of channels. This is done either by carefully assigning an already existing set of sequences for a given set of users or by mapping unconstrained sequences onto a unit circle. Secondly, we use an information theoretic approach to design the spreading sequences by matching the spectrum of each user’s sequence to the water-filling spectrum of the user’s channel. Finally, the design of inner shaping codes for single-head and multi-head magnetic recoding channels is discussed. The shaping sequences are designed considering them as short spreading codes matched to the recoding channels. The outer channel code is matched to the inner shaping code using the extrinsic information transfer chart analysis. In this dissertation we introduce a new frequency domain approach to design spreading sequences for frequency selective channels. We also extend this proposed technique to design inner shaping codes for partial response channels.

Thesis (Ph.D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 17, 2009). Includes bibliographical references.

Passive margins along the eastern seaboard of North America formed during early Mesozoic continental rifting and seafloor spreading, tectonic processes that are not fully understood. Seismic refraction and reflection data at the northeastern and north-central Gulf of Mexico and the Grand Banks of Newfoundland, Canada, are used to interpret the deep seismic velocity structure of sediments, crust, and mantle. These interpretations allow for a better understanding of continental rifting, mantle upwelling, magmatism, and seafloor spreading. Magma-poor rifting of the Newfoundland-Iberian margin developed a wide continent-ocean transition zone (COT). I present an analysis of 2-D marine seismic refraction and reflection data from the SCREECH project, including a shear velocity model to constrain the composition of the Newfoundland COT. Comparing SCREECH Line 2 Vp/Vs ratios with depth to potential lithologies supports a COT comprised of hyperextended continental crust and serpentinized mantle. Reconstructions of the opening of the Gulf of Mexico basin are impeded by a lack of seafloor magnetic anomalies and an abundance of sediments that obscure acquisition of seismic refraction datasets. Accordingly, the roles of mantle upwelling, magmatism, and lithospheric extension in this small ocean basin are poorly known. I present new 2-D marine seismic refraction data from the U.S. Gulf of Mexico collected during the 2010 GUMBO project. Rifting in the eastern Gulf of Mexico developed above a zone of anomalously high mantle potential temperatures that led to abundant magmatism. Syn-rift basins in continental crust, high velocity lower crust, a narrow zone of crustal thinning, and seaward-dipping reflectors support this interpretation. Oceanic crust here is thick despite slow seafloor-spreading rates, implying continuation of a thermal anomaly after rifting. In the north-central Gulf of Mexico, transitional crust is consistently thin (~10 km) across a wide zone. Velocity-depth comparisons, asymmetry of the north-central Gulf with the Yucatán margin, and dating of onshore xenoliths support either stretched and magmatically intruded continental crust or a multi-stage episode of seafloor spreading with ridge jumps. I contend that although tectonic inheritance may ultimately influence the location of a passive margin, the rifting process is largely controlled by mantle potential temperature and upwelling rate. / text

This dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations.Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver.Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated.We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading.Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies.

Spreading activation is a common method for searching semantic or neural networks, it iteratively propagates activation for one or more sources through a network { a process that is computationally intensive. Spectral association is a recent technique to approximate spreading activation in one go, and therefore provides very fast computation of activation levels. In this paper we evaluate the characteristics of spectral association as replacement for classic spreading activation in the domain of ontology learning. The evaluation focuses on run-time performance measures of our implementation of both methods for various network sizes. Furthermore, we investigate differences in output, i.e. the resulting ontologies, between spreading activation and spectral association. The experiments confirm an excessive speedup in the computation of activation levels, and also a fast calculation of the spectral association operator if using a variant we called brute force. The paper concludes with pros and cons and usage recommendations for the methods. (authors' abstract)

The collapse of buildings and infrastructure is an unfortunate consequence of major earthquakes (e.g., the 1964 Alaskan earthquake, the 1995 Kobe earthquake in Japan and the 2007 Pisco earthquake in Peru). Liquefaction-induced lateral spreading is known to be one cause of severe damage to deep foundation systems. However, the dynamic soil-structure interaction between liquefied soil and piles is extremely complex and further work is required to define the appropriate design pressures and to understand the mechanisms at work. This thesis presents the findings of an experimental program carried out using the large geotechnical centrifuge at C-CORE in St John’s Newfoundland, to investigate the mechanism of lateral spreading and its implications for dynamic soil-pile interaction. Soil and pile responses were measured using accelerometers, pore pressure transducers, and digital imaging using a high speed camera. Using these images, transient profiles of slope deformation were quantitatively measured using Particle Image Velocimetry (PIV). These tests illustrate the potential for earthquake shaking to excite the natural frequency of the liquefied soil column, which can lead to increased transient lateral pressures on piles in liquefiable ground. This study recommends that this potential for “auto tuning” should be anticipated in design and proposes a new limiting pseudo-static backbone p-y curve for use in the design of piles subjected to lateral spreading ground deformation. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-01-27 10:09:43.902