Distributed generation (DG) has received much attention recently due to environmental consciousness and rising of the energy efficiency. However, DG interconnecting to low-voltage distribution system may cause voltage variation, and a lot of single-phase DG or single-phase load may result in voltage unbalance. This thesis presents a distributed-STATCOM (D-STATCOM) to alleviate variation of both positive-sequence and negative-sequence voltages at the fundamental frequency. The D-STATCOM operates as susceptance and conductance at the fundamental positive-and negative-sequence frequency, respectively. The susceptance and conductance commands are dynamically tuned according to voltage fluctuation at the installation location. Therefore, the positive-sequence voltage can be restored to the nominal value as well as the negative-sequence voltage can be suppressed to an allowable level. Computer simulations and experimental results verify the effectiveness of the proposed control strategy.

Pendant les états naturels d'activité in vivo, les neurones neocorticaux sont sujets à une conductance membranaire forte et fluctuante. Cependant, les propriétés intégratives des neurones ne sont pas connues pendant ces états de “haute conductance” (HC). Nous avons (1) caractérisé le lien entre la dynamique des conductances et l'initiation du potentiel d'action (PA) dans les neurones corticaux dans les états HC; (2) comparé différents modèles de réponse de PA (PSTH) pendant ces états. Nous distinguons deux modes de décharge, selon que le PA est évoqué par une augmentation d'excitation ou par une diminution d'inhibition. Nous avons proposé une nouvelle méthode pour calculer les “spike-triggered average” (STA) des conductances à partir du Vm, testé cette méthode numériquement et in vitro, ainsi que appliqué cette méthode aux enregistrements in vivo. Nous démontrons que les PAs inhibiteurs sont majoritaires chez le chat éveillé, ce qui révèle un rôle majeur de l'inhibition.

Title from PDF of title page. / Document formatted into pages; contains 75 pages. / Thesis (M.S.C.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Analytical baseflow separation techniques such as those used in the automated hydrograph separation program HYSEP rely on a single input parameter that defines the period of time after which surface runoff ceases and all streamflow is considered baseflow. In HYSEP, this input parameter is solely a function of drainage basin contributing area. This method cannot be applied universally since in most regions the time of surface runoff cessation is a function of a number of different hydrologic and hydrogeologic basin characteristics, not just contributing drainage area. This study demonstrates that streamflow conductivity can be used as a natural tracer that integrates the different hydrologic and hydrogeologic basin characteristics that influence baseflow response. Used as an indicator of baseflow as a component of total flow, streamflow conductivity allows for an empirical approach to hydrograph separation using a simple mass balance algorithm. / ABSTRACT: Although conductivity values for surface-water runoff and ground-water baseflow must be identified to apply this mass balance algorithm, field studies show that assumptions based on streamflow at low flow and high flow conditions are valid for estimating these end member conductivities. The only data required to apply the mass balance algorithm are streamflow conductivity and discharge measurements. Using minimal data requirements, empirical hydrograph separation techniques can be applied that yield reasonable estimates of baseflow. This procedure was performed on data from 10 USGS gaging stations for which reliable, real-time conductivity data are available. Comparison of empirical hydrograph separations using streamflow conductivity data with analytical hydrograph separations demonstrates that uncalibrated, graphical estimation of baseflow can lead to substantial errors in baseflow estimates. / ABSTRACT: Results from empirical separations can be used to calibrate the runoff cessation input parameter used in analytical separation for each gaging station. In general, collection of stream conductivity data at gaging stations is relatively recent, while discharge measurements may extend many decades into the past. Results demonstrate that conductivity data available for a relatively short period of record can be used to calibrate the runoff cessation input parameter used for analytical separation. The calibrated analytical method can then be applied over a much longer period record since discharge data are the only requirement. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Studies of widely diverse species of a protein are a powerful tool to gain information on the structure and function of the protein. We investigated the response of human, pig, shark and killifish cystic fibrosis trans-membrane conductance regulator (CFTR) to specific inhibitors of the channel: CFTRinh-172, GlyH-101, and glibenclamide. In several expression systems, including isolated perfusions of the rectal gland, primary cell cultures of rectal gland tubules and oocyte expression, we observed fundamental differences in the sensitivity to inhibition by these CFTR blockers. We used primarily two-electrode voltage clamping of cRNA microinjected Xenopus laevis oocytes. In oocyte studies, shark CFTR was insensitive to CFTRinh-172 (maximum inhibition 8 ± 1.4% at 20µM), pCFTR was insensitive to Glibenclamide (maximum inhibition 12.8 ± 4.2% at 200µM), and all species were sensitive to GlyH-101 (maximum inhibition with pCFTR of 80.2 ± 3.6% at 20µM). Shark CFTR was completely insensitive to inhibition by CFTRinh-172 in short circuit current experiments (2.5 ± 0.15 % inhibition of chloride secretion) compared to inhibition with GlyH-101 (56.5 ± 6.56 % inhibition of chloride secretion). Perfusion studies confirmed these results. These experiments demonstrate a profound difference in the sensitivity of different CFTR species to inhibition by CFTR blockers. However, the amino acid residues that have been proposed by site directed mutagenesis studies to be responsible for inhibitor binding are uniformly conserved in all four isoforms studied. Therefore, the differences cannot be explained by simply targeting one amino acid for site-directed mutagenesis. Rather, the potency of the inhibitory actions of CFTRinh-172, Gly-H101 and glibenclamide on the CFTR molecule is dictated by the local environment and the three dimensional structure of residues that form the vestibule and the chloride pore.

Fear conditioning and extinction are central in the cognitive behavioral model of obsessive-compulsive disorder (OCD), which underlies exposure-based cognitive behavioral therapy (CBT). Youth with OCD may have impairments in conditioning and extinction that carries treatment implications. The present study examined these processes using a differential conditioning paradigm. Forty-one youth (19 OCD, 22 community controls) and their parents completed a battery of clinical interviews, rating scales, and a differential conditioning task. Skin conductance response (SCR) served as the primary dependent measure across all three phases of the conditioning procedure (habituation, acquisition, and extinction). During habituation, no meaningful differences were observed between groups. During acquisition, differential fear conditioning was identified across groups evidenced by larger SCRs to the CS+ compared to CS-, with no significant group differences. During extinction, a three-way interaction and follow-up tests revealed youth with OCD failed to exhibit differential fear conditioning during early fear extinction; whereas community controls consistently exhibited differential fear conditioning throughout extinction. Across participants, the number and frequency of OCD symptoms was positively associated with fear acquisition and negatively associated with fear extinction to the conditioned stimulus. OCD symptom severity was negatively associated with differential SCR in early extinction. Youth with OCD exhibit a different pattern of fear extinction relative to community controls that may be accounted for by impaired inhibitory learning in early fear extinction. Findings suggest the potential benefit of augmentative retraining interventions prior to CBT. Therapeutic approaches to utilize inhibitory-learning principles and/or engage developmentally appropriate brain regions during exposures may serve to maximize CBT outcomes.

Reliable prediction of climate change and its impact on and feedbacks from terrestrial carbon cycles requires realistic representation of physiological and ecological processes in coupled climate-carbon models. This is hampered by various deficiencies in model structures and parameters. The goal of my study is to improve model realism by incorporating latest advances of fundamental eco-physiological processes and further to use such improved models to investigate climate-carbon interactions at regional to global scales. I focus on the CO₂ diffusion within leaves (a key plant physiological process) and large-scale disturbances (a fundamental ecological process) as extremely important but not yet in current models. The CO₂ diffusion within plant leaves is characterized by mesophyll conductance (g[subscript m]), which strongly influences photosynthesis. I developed a g[subscript m] model by synthesizing new advances in plant-physiological studies and incorporated this model into the Community Land Model (CLM), a state-of-art climate-carbon model. I updated associated photosynthetic parameters based on a large dataset of leaf gas exchange measurements. Major findings are: (1) omission of g[subscript m] underestimates the maximum carboxylation rate and distorts its relationships with other parameters, leading to an incomplete understanding of leaf-level photosynthesis machinery; (2) proper representation of g[subscript m] is necessary for climate-carbon models to realistically predict carbon fluxes and their responsiveness to CO₂ fertilization; (3) fine tuning of parameters may compensate for model structural errors in contemporary simulations but introduce large biases in future predictions. Further, I have corrected a numerical deficiency of CLM in its calculation of carbon/water fluxes, which otherwise can bias model simulations. Large-scale disturbances of terrestrial ecosystems strongly affect their carbon sink strength. To provide insights for modeling these processes, I used satellite products to examine the temporal-spatial patterns of greenness after a massive ice storm. I found that the greenness of impacted vegetation recovered rapidly, especially in lightly and severely impacted regions. The slowest rebound occurred over moderately impacted areas. This nonlinear pattern was caused by an integrated effect of natural regrowth and human interventions. My results demonstrate mechanisms by which terrestrial carbon sinks could be significantly affected and help determine how these sinks will behave and so affect future climate. / text

A mechanically controllable break junction setup was designed, constructed and characterized. The mechanically controllable break junction technique is commonly used for measurement of quantum conductance of metals and single molecule conductance. The technique relies on resistance to external vibrations disrupting the atomic or molecular junctions formed and should be in a low electronic noise environment. Through a series of experiments the setup was found to have high mechanical stability and low electronic noise. The quantum conductance of gold was measured repeatedly and a histogram was plotted showing good agreement with the literature. The results indicate that with modifications, the setup can be used to measure the conductance of single molecule junctions and single molecule thermoelectric properties.

Research was conducted to determine individual suitability of native and Canadian-bred selected plants in terms of growth and survivability for local extensive green roofs. The experiment was single-factor (species) with 12 levels (two Sedum spp. [controls]; 10 Canadian-bred or native plant species) in a randomized complete block design with three blocks. Variables measured were percent survival and cover, height, fresh and dry weights, stomatal conductance, transpiration, photosynthetic rate, soil temperature, soil moisture, and reflectance. Artemisia stelleriana contributed more to cooling through transpiration than Sedum floriferum, and maintained similar soil moisture to Sedum acre. Lotus corniculatus was similar to the controls in photosynthetic rate and had higher reflectance than Sedum acre in July. With high biomass and photosynthetic rates, Aster novi-belgii may contribute more to carbon sequestration and insulation than the controls. Artemisia stelleriana , Lotus corniculatus, and Aster novi-belgii are suitable species for extensive green roofs in northern Nova Scotia.

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