VictorJuiz/thesis huggingface dataset:
Statistical mechanics of the adsorption and collapse transitions in polymers

Two different models of a polymer molecule in a dilute solution near an adsorbing interface are studied. The first one consists of a self-interacting self-avoiding walk on the cubic lattice terminally attached to and interacting with the impenetrable 'z' = 0 plane. The second one employs a self-interacting self-avoiding walk on the cubic lattice terminally attached to and interacting with the penetrable 'z' = 0 plane. A number of results about the form of the free energy and the form of the phase diagram are derived for such walks, and for similarly defined polygons, using rigorous mathematical arguments. The second part of the thesis consists of a numerical treatment of this problem using a highly efficient Monte Carlo algorithm. Conjectured phase diagrams for the penetrable plane case and the impenetrable plane case are given and compared with each other.
Plasticity in the adult human somatosensory thalamus

Representational plasticity has been well documented in experimental animals. However in humans, somatotopographic reorganization has only been anecdotally observed. Recent studies have suggested that cortical representation of body parts can change in humans; however the extent of reorganization is unknown and no attempts have been made to determine the contribution of subcortical structures to cortical plasticity. The aim of this thesis was to determine (i) whether plasticity exists in the human at the thalamic level and (ii) what the possible mechanisms involved are. 'I'. Long-term deafferentation was associated with different patterns of thalamic organization as determined by receptive (RF) and projected field (PF) mapping. In patients with leg/foot deafferentation there was an expansion of "trunk" representation and 4 of 5 limb amputees displayed an enlarged stump representation. Patients with face deafferentation had a significantly larger region of thalamus from which microstimulation evoked PFs on the face. 'II'. Two mechanisms have been proposed to account for such alterations in representation: sprouting of new connections and unmasking of previously present, relatively ineffective connections. The unmasking hypothesis was investigated by temporarily deafferenting cells with RFs located on the lidocaine-blocked digit. Most of these neurons displayed an improvement in, or an appearance of, new responses to mechanical stimulation of adjacent digits. 'III'. To identify the relatively ineffective connections responsible for this phenomenon, the RFs of single units and nearby sites were subjected to electrical stimulation (ES) and in some cases repetitive mechanical stimulation (RMS). Responses from within the RF were excitatory and of short latency (SLRs, 20 ms). Most cells (87%) responded to ES and RMS applied outside their RF and these responses were of long latency (LLRs, 42 ms), although some showed both SLRs and LLRs. 'IV'. Excessive cutaneous stimulation of one skin surface has also resulted in alterations in representation in the cortex of experimental animals. Patients with tremor, or increased afferent input to movement-related neurons, were found to have a larger region of movement-related representation. Despite limited thalamic exploration and the inherent problems with data collection in patients, when I-IV are examined together and interpreted in light of animal models, one can conclude that plasticity is indeed possible in the human somatosensory system and present at the thalamic level. The clinical importance of plasticity may be two-fold: both beneficial in that it may aid recovery from injury and detrimental in its possible maintenance of pain and tremor. (Abstract shortened by UMI.)
Protein interactions in E2F1-mediated transcriptional activation

Transcriptional activators of RNA polymerase II bind promoter regions of genes and regulate mRNA synthesis through protein interactions with components of the transcription apparatus. In chapter two I describe the first characterization of interactions between transcriptional activators and the general transcription factor TFIIH. In particular, the herpes virion protein VP16 and the tumour suppressor protein p53 are both shown to bind yeast TFIIH. The human transcriptional activator E2F1 regulates gene expression at the G1/S boundary of the cell cycle, and chapters three and four contain an analysis of the E2F1 activation domain. Using protein affinity chromatography, I have shown that the activation domain of E2F1 binds the human and yeast multi-subunit general transcription factors TFIID and TFIIH. E2F1 binds the yeast and human TATA-box binding protein (TBP) of TFIID, and also binds the p62 and p89 subunits of human TFIIH, and the yeast homologue of p62, TFB1. Deletions and single amino acid substitutions of E2F1 were analyzed for their effect on TFIIH- and TFIID-binding. There are two distinct binding sites in E2F1 for TBP (amino acids 386-417 and 415-437), and one for TFIIH (409-437), which overlaps both TBP-binding sites. Mutant proteins were expressed as fusions to the DNA-binding domain of the yeast transcription factor GAL4, and tested for transcriptional activation in tissue culture. Each minimal TBP-binding site activates transcription, while fragments of E2F1 that do not bind TBP cannot activate. A mutation in E2F1 that enhances TFIIH-binding results in an increase in activation, however TFIIH-binding is not required for activation. These results strongly suggest that the interactions between E2F1 and both TBP and TFIIH contribute to transcriptional activation by E2F1. The retinoblastoma protein (Rb) binds E2F1 and inhibits its ability to activate transcription. In chapter five, Rb is shown to compete with both TBP and p62 for binding to E2F1. A tumorigenic form of Rb that is deficient in its ability to inhibit EM-mediated activation is also deficient in competing with TBP for binding to E2F1. This supports a model in which Rb inhibits E2F1-mediated transcriptional activation by blocking interactions between E2F1 and both TFIID and TFIIH.
Phase sweeping transmit diversity with fading resistant constellations

The problem of slow fading in the forward link of a mobile radio system is addressed in this thesis. Transmit diversity at the base station is investigated as a solution to mitigating the long term impairment. A diversity system is proposed in which multiple antennas spaced far apart transmit simultaneously the same signal to the mobile terminal. The objective is to create artificial fast fading in an otherwise static environment. A channel coding scheme is devised which exploits the autocorrelation properties of the resulting fading envelope. By matching the frequency offset of the carriers to the interleaving depth of the channel coder, it is possible to realize antenna diversity gain at low mobile velocities and coding gain at high velocities. Simulations demonstrate the feasibility of increasing the diversity order of the forward link under slow fading conditions without having to maintain a condition of orthogonality between the multiple transmissions.
Digital radiology using active matrix readout of amorphous selenium

The concept of a direct, real-time, flat-panel detector is being investigated for digital radiology. The detector employs a layer of x-ray sensitive photoconductor ('e.g.' amorphous selenium) to directly convert x-rays to charge, and a large area integrated circuit called an 'active matrix' which consists of a two dimensional array of thin film transistors (TFTs) for electronic image readout. The readout can be performed in real-time (30 frames per second) and thus can be applied in both radiography and fluoroscopy. The advantages of the direct, flat-panel detector include: instantaneous image readout, compact size in the form of a cassette, efficient use of x-rays to produce high quality x-ray images, and freedom from geometric image distortion. This work investigates practical solutions for making a high quality and reliable flat panel detector. The two factors affecting the reliability of the detector are: radiation hardness of TFTs and operation of the detector under the high voltage applied to the x-ray photoconductor. The image quality of the detector is measured in terms of detective quantum efficiency (DQE) at all spatial frequencies. The radiation hardness of TFTs is measured at the life-time dose expected for a diagnostic x-ray imaging detector. The dominant effect of radiation is the negative shift of the TFT threshold voltage by less than 1 V, which is insufficient to affect the normal operation of the TFTs. Thus the radiation hardness of TFTs is adequate for diagnostic x-ray imaging. In order to assure a safe and reliable operation of TFTs under the high voltage bias to the x-ray photoconductor, a novel dual-gate TFT structure with self-protection against high voltage damage is proposed and investigated. The results show that an existing dual-gate TFT design can provide satisfactory high voltage protection for all radiographic applications. The DQE of the detector as a function of spatial frequency was studied both theoretically using a cascaded linear systems model, and experimentally with a prototype detector with 160 [mu]m pixel pitch. The results obtained using the theoretical model agree with those obtained from experimental measurements. Detector design parameters affecting the DQE are identified and strategies for maximizing DQE are proposed.
Tip velocity tracking control for elastic manipulators

A unique approach to tip velocity control of an elastic robotic manipulator is presented. This method has potential application in teleoperation control and in applications where the trajectory is generated in real-time. Control is effected by reducing the tip velocity tracking error between the desired tip velocity and the measured tip velocity. Thus, in teleoperation, the concept of dead reckoning is used, so that while the manipulator's desired tip velocity is specified, the goal is for the tip to follow a path, leading toward a desired terminal position. This is done by concentrating the controller's effort on the manipulator tip while allowing the manipulator's links to deform., The controller utilizes a gain scheduling scheme to arrive at an appropriate feedback law. The control algorithm is implemented using a parallel-processing scheme on a multiprocessor system which consists of INMOS Transputers® . Experimental results are obtained using Radius, the Space Robotics Laboratory Facility at the University of Toronto Institute for Aerospace Studies. Radius was designed to serve specifically as a test-bed for the development and evaluation of control methods for elastic manipulators. For the present work Radius is configured as a two-link manipulator with both links structurally flexible. One of the trajectories used for the simulations and experiment is a square, which is quite difficult for an elastic manipulator to execute. This box trajectory is more demanding than trajectories typically executed by Canadarm and so link elasticity becomes an important consideration. The effect of elasticity is demonstrated using an independent joint PD controller. In simulation, excellent tip velocity tracking was achieved using the proposed controller. In the experiment, reasonable accuracy in following the desired tip path was attained, however, disturbances, mainly a result of unmodeled joint dynamics, caused degraded performance. The controller may be improved by making it more robust to disturbances and by adding control terms to assist in minimizing the tip position tracking error. Notable contributions include the design, parallelization, and parallel implementation of the tip velocity tracking controller. In addition, experimental results were obtained and a preliminary stability investigation of the controller was done.
Flash photolysis generation and reactivities of biphenylylnitrenium ions and phenylcyclohexadienyl cations

A series of substituted 4-azidobiphenyls have been subjected to flash photolysis irradiation in 20% acetonitrile:water. The corresponding 4-biphenylyinitrenium ions are observed and first-order rate constants for their reactions with solvent (kw) have been measured. The plot of the solvent reactivities for the X'-substituted derivatives 'versus' [sigma] + exhibit a poor correlation, with the points for the para [pi]-electron donors deviating in the direction of requiring a more negative [sigma] + value. The data are more satisfactorily fit to the two-parameter Yukawa-Tsuno equation; the parameter r+ obtained for this fit is 2.8. This is similar to the situation that has been previously observed with benzylic-type carbenium ions. The conclusion is made that in their reaction with water, 4-biphenylylnitrenium ions behave like benzyl cations bearing two additional stabilizing vinyl groups, i.e. as if they had the structure Ar-C+(C=C)2. The nitrenium ions are quenched by azide ion, 2' -deoxyguanosine (dG), and ethyl vinyl ether and second-order rate constants kNu for these reactions are measured. The plots of k Nu 'versus' kw indicate that these quenching reactions approach the diffusion limit for the first two nucleophiles. The ratios kdG/kw for most of these nitrenium ions are larger than 103 M-1, indicating a high selectivity for the nucleoside. A 6,6-dimethyl-3-phenylcyclohexadienyl cation (45) has been generated in the ground state from three precursors in 20% acetonitrile:water: in the solvolysis of 6,6- dimethyl-3-phenylcydohexa-2,4-dien-1-yl acetate (46) or from the isomeric alcohols 4,4-dimethyl-1-phenylcyclohexa-2,5-dien-1-ol (61) and 6,6-dimethyl-1- phenylcyclohexa-2,4-dien-1-ol ( 62) under acidic conditions. Although attempts to detect the cation by flash photolysis of 46 and 61 were unsuccessful, a cation-like transient (71, ks = 6.92 * 10 4 s-1, kaz = 5 * 109 M-1s-1) has been observed by employing 4,4-dimethyl-1-(3',5'-dimethoxyphenyl)cyclohexa-2,5-dien-1-ol (47) as precursor. The overall analysis shows that the conjugated alcohol 62 is both the kinetic and thermodynamic product of the addition of water to 45. These results are compared with ones for the 4-biphenylyinitrenium ion (15), in terms of its cyclohexadienyl cation resonance contributors. 45 is slightly more stable than 15 in aqueous solutions. The two differ significantly in site preference of water addition as the kinetic product with 15 is the unconjugated alcohol. It is suggested that the electronegative nitrogen of 15 results in greater fraction of the positive charge being localized at the remote para carbon, so that is the site where water preferentially reacts.
Intracellular traffic of the insulin-responsive glucose transporter GLUT4

Insulin stimulates glucose transport into skeletal muscle, heart and adipose tissues by acutely increasing the cell surface expression of the GLUT4 glucose transporter. This is achieved by a mobilization of preformed, intracellularly sequestered GLUT4 transporters to the cell surface, in addition to reducing the rate of internalization from the cell surface. Two main aspects of this process were examined in this thesis: (1) the mechanism by which GLUT4 vesicles may recognize, dock and subsequently fuse with the cell surface, and (2) the mechanism by which GLUT4 endocytosis, is regulated. Intracellular GLUT4 vesicles in 3T3-L1 adipocytes are shown to contain the v-SNARE proteins cellubrevin and VAMP-2 These proteins are required for vesicle secretion in many systems and are shown here to be involved in GLUT4 exocytosis to the cell surface. These proteins are also shown to be expressed in muscle and muscle cells in culture where they may have a similar role. VAMP proteins are shown to interact with the t-SNARE syntaxin 4 which is found to be expressed primarily at the cell surface of 3T3-L1 adipocytes. Functional studies suggest that syntaxin 4 is also required for insulin-stimulated GLUT4 exocytosis. GLUT4 endocytosis from the cell surface is thought to occur via the clathrin-dependent endocytic system. By perturbing dynamin/amphiphysin interactions the endocytosis of GLUT4 is shown to be inhibited, suggesting that these proteins are involved in GLUT4 retrieval from the cell surface. Dynamin II may potentially have a regulatory role in GLUT4 endocytosis as insulin affects the association of dynamin with the plasma membrane. In conclusion, the SNARE proteins VAMP-2, cellubrevin and syntaxin 4 are involved in GLUT4 exocytosis while dynamin II participates in the endocytosis of this transporter.
Frequenin in crustaceans, cloning and immunolocalization

Crustaceans provide many advantages in the study of synaptic transmission and plasticity. Neuromuscular preparations have been well characterized in terms of long-term facilitation, synaptic depression and long-term adaptation. In addition, crustacean motor neurons are excellent models to study the differentiation into 'phasic' and 'tonic' motor neurons. These two types of motor neurons differ substantially in their transmitter release properties. Although the ultrastructural and biochemical differences between these neurons have been well studied, very little is known about possible molecular factors underlying this differentiation. The neuronal calcium-binding protein frequenin has been shown to enhance synaptic efficacy at neuromuscular junction in Drosophila and Xenopus and could serve as such a molecular factor. Standard molecular biology techniques were used to clone frequenin from lobster and crayfish. The lobster and crayfish frequenins were found to be closely related to originally identified Drosophila frequenin. In addition, immunolocalization of frequenin at the crayfish neuromuscular junction revealed that frequenin is heavily expressed in 'phasic' and less strongly in 'tonic' motor neurons.
A low-power low-voltage second-order [Sigma Delta] modulator

With the increasing demand for mobile communications, there has been a push for micropower circuits to achieve long battery life. At the front end of most communication systems is an analog-to-digital converter. This thesis presents work done on the implementation of a low-power low-voltage second order $\Sigma\Delta$ modulator in a 1V, 0.5 $\mu$m CMOS process. To minimize power and area, the design must limit its component count by keeping the order of the design to a minimum. However, the circuit must also provide sufficient dynamic range and resolution to render itself useful for voice applications. A fully-differential second order switched-capacitor architecture was chosen for this design as it strikes a balance between competing factors such as power, area, and performance. The modulator consists of three major components: the op-amp, the comparator-latch, and the clock generator. The limiting factor in the performance of the modulator is the performance of the fully differential op-amp, which is a folded cascode design to minimize transistor stacking and to maximize voltage swing and gain in a low voltage environment. It can achieve a DC gain of 97 dB with a settling time of 170 ns. Behavioural and post layout simulation show that at a 2 MHz sampling rate, this design is capable of achieving a nominal bandwidth of 7 kHz with a dynamic range of 14-bits while dissipating a total power of 425 $\mu$W.
John Henry Newman on education

In 'The Idea of a University', Newman's gentleman followed the humanist tradition of Aristotle's man of general culture who understands issues from a knowledge of the principles involved and approaches areas of truth only through the particular methods which make them properly accessible. Parallels between the 'Nicomachean Ethics' and 'The Idea of a University' establish this common ground. Newman's own example illustrates the way a knowledge of fundamental principles and methods resolves ambiguities and links theories to their consequences: for example, his distinction between science and moral and religious truth in "The Tamworth Reading Room"; his differentiation between liberal and useful education in ' The Idea of a University' his description in the 'Grammar of Assent' of the 'organon' through which we know indemonstrable truth; his separation of religious formation from the cultivation of the intellect because religious formation pertains to conscience and is mediated through such channels as sacraments, preaching, and the model of others. A comparison of Newman and Bacon, two arbiters of method, confirms the importance to both of applying methods only to those areas of truth which they serve to illuminate: physical science, social matters, and God. However, in 'The Advancement of Learning', in order to redirect learning towards useful knowledge and material well-being, Bacon dismisses speculative truth, the traditional field of humanist learning and the centrepiece of liberal education. This reorientation of learning influenced subsequent educational theories which increasingly recognized only the method of observation and experiment in all areas of learning including language. As a first principle in education, Newman assumes an objective, intelligibly unified world. The similarity between Newman's point of departure and traditional humanist education is evident in the commonalities between Quintilian's ' On the Early Education of the Citizenorator' and Newman's views on education particularly as described in 'The Catholic University Gazette '. Unlike Baconian theories of education, liberal education for the man of general culture recognizes the distinction between the rhetorical mode of thought required by letters and methodical or philosophical reasoning from principles. Humanist training coupled with moral and religious formation develop the Christian humanist gentleman.
Saccades to doubly-flashed targets

The effect of a second pulse on saccadic performance was examined by asking the subject to track a stimulus, and measuring the resulting saccade. The latency data was examined with a bootstrapping method to determine objectively the modality of the population; the results were that the majority of them were unimodal; however, because a sizeable portion of the histograms also showed "shoulders" at similar latencies, the possibility of sub-populations could not be eliminated. The effect of the second pulse was also examined by comparing the cumulative histograms of each of the two-pulse conditions with the one of the single pulse configurations (SP) and with a model which gave the latency distribution expected from a two-pulse stimulus if the two pulses were processed independently by the saccadic system. The results showed the effect of the second pulse differed greatly depending on which yardstick was used.