Automotive Radars have introduced various functions on automobiles for driver’s safety and comfort, as part of the Intelligent Transportation System (ITS) including Adaptive Cruise Control (ACC), collision warning or avoidance, blind spot surveillance and parking assistance. Although such radar systems with 24 GHz carrier frequency are already in use but due to some regulatory issues, recently a permanent band has been allocated at 77-81 GHz, allowing for long-term development of the radar service. In fact, switchover to the new band is mandatory by 2014. A frequency multiplier will be one of the key components for such a millimeter wave automotive radar system because there are limitations in direct implementation of low phase noise oscillators at high frequencies. A practical way to build a cost-effective and stable source at higher frequency is to use an active multiplier preceded by a high spectral purity VCO operating at a lower frequency. Recent improvements in the performance of SiGe technology allow the silicon microelectronics to advance into areas previously restricted to compound semiconductor devices and make it a strong competitor for automotive radar applications at 79 GHz. This thesis presents the design of active frequency doubler circuits at 20 GHz in a commercially available SiGe BiCMOS technology and at 40GHz in SiGe bipolar technology (Infineon-B7h200 design). Buffer/amplifier circuits are included at output stages to drive 50 Ω load. The frequency doubler at 20 GHz is based on an emitter-coupled pair operating in class-B configuration at 1.8 V supply voltage. Pre-layout simulations show its conversion gain of 10 dB at -5 dBm input, fundamental suppression of 25dB and NF of 12dB. Input and output impedance matching networks are designed to match 50 Ω at both sides. The millimeter wave frequency doubler is designed for 5 V supply voltage and has the Gilbert cell-based differential architecture where both RF and LO ports are tied together to act as a frequency doubler. Both pre-layout and post-layout simulation results are presented and compared together. The extracted circuit has a conversion gain of 8 dB at -8 dB input, fundamental suppression of 20 dB, NF of 12 dB and it consumes 42 mA current from supply. The layout occupies an area of 0.12 mm2 without pads and baluns at both input and output ports. The frequency multiplier circuits have been designed using Cadence Design Tool.

Soil salinity is a widespread problem that limits crop yield throughout the world. The accumulation of soluble salts in the soil can inhibit plant growth by increasing the osmotic potential of interstitial water, inducing ion toxicity and nutrient imbalances in plants. Over the last decade, considerable effort has been put into developing economical and effective methods to reclaim these damaged soils. Phytoremediation is a technique that uses plants to extract, contain, immobilize and degrade contaminants in soil. The most common process for salt bioremediation is phytoextraction which uses plants to accumulate salt in the shoots, which is then removed by harvesting the foliage. As developing significant plant biomass in saline soils is an issue, a group of free-living rhizobacteria, called plant growth promoting rhizobacteria (PGPR), can be applied to plant seeds to aid plant growth by alleviating salt stress. The principle objective of this research was to test the efficacy of PGPR in improving the growth of plants on salt-impacted soils through greenhouse and field studies. In this research, previously isolated PGPR strains of Pseudomonas putida. UW3, Pseudomonas putida UW4, and Pseudomonas corrugata CMH3 were applied to barley (Hordeum valgare C.V. AC ranger), oats (Avena sativa C.V. CDC baler), tall wheatgrass (Agropyron elongatum), and tall fescue (festuca arundinacea C.V. Inferno). PGPR effects on plant growth, membrane stability, and photosynthetic activity under salt stress were examined. Greenhouse studies showed that plants treated with PGPR resulted in an increase in plant biomass by up to 500% in salt-impacted soils. Electrolyte leakage assay showed that plants treated with PGPR resulted in 50% less electrolyte leakage from membranes. Several chlorophyll a fluorescence parameters, Fv/Fm, effective quantum yield, Fs, qP, and qN obtained from pulse amplitude modulation (PAM) fluorometry showed that PGPR-treated plants resulted in improvement in photosynthesis under salt stress. Field studies showed that PGPR promoted shoot dry biomass production by 27% to 230%. The NaCl accumulation in plant shoots increased by 7% to 98% with PGPR treatment. The averaged soil salinity level at the CMS and CMN site decreased by 20% and 60%, respectively, during the 2008 field season. However, there was no evidence of a decrease in soil salinity at the AL site. Based on the improvements of plant biomass production and NaCl uptake by PGPR observed in the 2008 field studies, the phytoremediation efficiency on salt-impacted sites is expected to increase by 30-60% with PGPR treatments. Based on the average data of 2007 and 2008 field season, the time required to remove 25% of NaCl of the top 50 cm soil at the CMS, CMN and AL site is estimated to be six, twelve, and sixteen years, respectively, with PGPR treatments. The remediation efficiency is expected to accelerate during the remediation process as the soil properties and soil salinity levels improve over time.

Quorum sensing (QS) cell-cell communication systems are utilized by bacteria to coordinate their behaviour according to cell density. Several different types of QS signal molecules have been identified, among which acyl-homoserine lactones (AHLs) produced by Proteobacteria have been studied to the greatest extent. QS has been shown to be involved in many aspects of bacterial life, including virulence, bioluminescence, symbiosis, antibiotic production, swarming and swimming motility, biofilm formation, conjugation and growth inhibition. Although QS has been studied extensively in cultured microorganisms, little is known about the QS systems of uncultured microorganisms and the roles of these systems in microbial communities. To extend our knowledge of QS systems and to better understand the signalling that takes place in the natural environment, in the first part of this thesis, isolation and characterization of new QS systems from metagenomic libraries constructed using DNA from activated sludge and soil were described. Using an Agrobacterium biosensor strain, three cosmids (QS6-1, QS10-1 and QS10-2) that encode the production of QS signals were identified and DNA sequence analysis revealed that all three clones encode a novel luxI family AHL synthase and a luxR family transcriptional regulator. Thin layer chromatography revealed that these LuxI homolog proteins are able to synthesize multiple AHL signals. Tandem mass spectrometry analysis revealed that LuxIQS6-1 directs the synthesis of at least three AHLs, 3-O-C14:1 HSL, 3-O-C16:1 HSL and 3-O-C14 HSL; LuxIQS10-1 directs the synthesis of at least 3-O-C12 HSL and 3-O-C14 HSL; while LuxIQS10-2 directs the synthesis of at least C8 HSL and C10 HSL. Two possible new AHLs, C14:3 HSL and (?)-hydroxymethyl-3-O-C14 HSL, were also found to be synthesized by LuxIQS6-1. Agrobacterium tumefaciens is a plant pathogen that causes crown gall disease. Its ability to transfer and integrate foreign DNA into plant genome also makes it a useful tool for plant genetic engineering. Ethylene, the gaseous plant hormone, has been reported to be important for both crown gall development and A. tumefaciens mediated transformation efficiency to plants. ACC deaminase, an enzyme that can break down ACC, the direct precursor of ethylene biosynthesis in plants, is a mechanism used by some plant growth promoting bacteria (PGPB) to promote plant growth by reducing stress ethylene levels. In the second part of this thesis, the effect of ACC deaminase on A. tumefaciens induced crown gall development and on A. tumefaciens mediated transformation efficiency was studied. By either introduction of an ACC deaminase encoding gene into the virulent strain A. tumefaciens C58 or co-inoculation of A. tumefaciens C58 with an ACC deaminase containing PGPB P. putida UW4, using different plant systems including tomato plants and castor bean plants, it was found that the presence of an ACC deaminase significantly inhibited crown gall development. It was also found that introduction of an acdS gene into the disarmed A. tumefaciens strain GV3101::pMP90 reduced the ethylene levels evolved by plants during infection and cocultivation process and increased the transformation efficiency of commercialized canola cultivars. The A. tumefaciens D3 strain was reported to contain an ACC deaminase encoding gene (acdS). In this study it was determined that this strain is an avirulent strain and shows plant growth promoting activity. When co-inoculated with A. tumefaciens C58 on castor bean stems, both the wild type and the acdS knockout mutant showed biocontrol activity and were able to significantly inhibit crown gall formation, with the wild type strain showing slightly better tumor inhibition effects. The mutation of acdS and its regulatory gene lrpL in A. tumefaciens D3 was also found to affect QS signal production of this strain, which indicates a cross talk between the two sets of genes.

According to our previous results, ethephon-induced sweet potato leaf senescence and senescence-associated gene SPCP1 expression was affected by reduced glutathione, EGTA, and cycloheximide (Chen et al., 2009). These data suggest that calcium influx, reactive oxygen species (ROS) and de novo synthesized proteins can affect ethephon-mediated effects. Therefore, PCR-selective substractive hybridization and RACE-PCR methods were used to clone 5 full-length cDNAs encoded putative calmodulin (SPCAM), catalase (SPCATA), anionic peroxidase (SPPA), ACC oxidase (SPACO), and DSS1-like protein (SPDSS1) from mixed samples of ethephon-treated leaves for 6 and 24 hours. The ORF of SPCAM contains 450 nucleotides and encodes 149 amino acids. There are 4 putative EF-motifs in the deduced protein structure. SPCAM exhibited amino acid sequence identity with isolated Arabidopsis calmodulins from 48% to 100%, and was completely the same as CaM7 calmodulin. The ORF of SPCATA contains 1479 nucleotides and encodes 492 amino acids. SPCAM exhibited high amino acid sequence identity with other plant catalases from 71.2% to 80.9%, and had the highest identity with mangrove catalase. The ORF of SPPA contains 1068 nucleotides and encodes 355 amino acids. SPPA exhibited amino acid sequence identity with other published sweet potato peroxidase isoforms from 28.7% to 97.5%, and had the highest identity with anionic peroxidase SWPA4. The ORF of SPACO contains 930 nucleotides and encodes 309 amino acids. SPACO exhibited high amino acid sequence identity with other plant ACC oxidases from 62.3% to 81.5%, and had the highest identity with tobacco ACC oxidase. The ORF of SPDSS1 contains 228 nucleotides and encodes 75 amino acids. SPDSS1 exhibited amino acid sequence identity with other DSS1 from 25.2% to 62.3%, and had the highest identity with maize DSS1. The chlorophyll contents and Fv/Fm values were significantly reduced, however, the isolated gene expression was remarkably enhanced in natural senescent leaves. DAB staining showed that H2O2 amount was remarkably elevated at S3 senescent leaves compared to leaves of the other developmental stages. Evan blue staining also demonstrated that S3 senescent leaf had more cell death compared to S0 young leaves. In addition ethephon-induced leaf senescence exhibited similar results. The chlorophyll contents and Fv/Fm values were significantly reduced, however, the isolated gene expression was remarkably enhanced in ethephon-treated leaves compared to dark control. DAB staining showed that H2O2 amount was remarkably elevated at 72 hours in ethephon-treated leaves compared to dark control. Evan blue staining also demonstrated that ethephon-treated leaf for 72 hours had more cell death compared to dark control. Based on these data we conclude that SPCAM, SPCATA, SPPA, SPACO and SPDSS1 gene expression were significantly increased in natural and ethephon-induced senescent leaves. The possible functions of these isolated genes in association with events in ethephon-induced leaf senescence, including calcium influx, ROS elevation or scavenge, and following signaling will be discussed.

Plant-wide communication between tissues and cells is organized, in part, by a suite of compounds called hormones. I have chosen to focus on the effects of one plant hormone, ethylene; how its synthesis is controlled and how its perception is mediated to differentially control cell development and response to pathogens. In the production of ethylene, one level of control is by modulating the levels of the immediate precursor to ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC). I characterize here a plant encoded gene homologous to bacterial ACC Deaminases, AtACD1, and show through up- and down-regulation of the gene that it can modulate the plants sensitivity to exogenous ACC. Once ethylene is produced, it is sensed in Arabidopsis thaliana by a family of 5 receptors. I show that ETR2 in Arabidopsis is responsible for modulation of the microtubule cytoskeleton assembly as loss-of –function mutations to this gene cause randomized microtubule assembly in trichomes and increase sensitivity to microtubule depolymerising drugs in root hairs. In studies of plant:pathogen interactions, ethylene is a central signaling agent required for plant resistance. While it has been shown that etr1 mutants show increased susceptibility to fungal pathogens, exogenous ethylene has also been shown to speed the progress of pathogenesis. Using Fumonisin B1 (FB1) to induce cell death I show that etr1-1 has accelerated cell death while ein4-1 has a reduced rate of necrosis. Further to this, mutations to the other three ethylene receptors do not have any effect on the rate of cell death. My interest in cell development led to the characterization of an activation tagged Populus tremula x P. alba line with increased trichome initiation. The gene responsible for these phenotypes was identified as PtMYB186, which also affected growth rate, transpiration rate, photosynthetic capacity, and resistance to the Tussock moth larvae. Together these studies provide a new framework for our understanding of how the ethylene signal is modulated in plants and the controls behind cellular development. This knowledge will help reconcile studies which show that ethylene has different effects on plant development and provide new avenues of research into trichome development. / Thesis (Ph.D, Biology) -- Queen's University, 2009-01-13 10:08:03.605

Neural activity within the brain underlies complex behavior that allows us to interact with our environment. The anterior cingulate cortex (ACC) is believed to mediate appropriate behavioral responses by integrating emotional and cognitive information about external stimuli. If this understanding is correct, then neural activity within the ACC must therefore correlate with behavioral output in response to external experience. The aim of this thesis is to bridge mechanisms identified in vitro with behaviors observed in vivo to determine the neural substrates of ACC mediated behavior. This thesis focuses on glutamatergic receptors that have been established as mediators of excitatory transmission in the ACC. Through a combination of behavioral, pharmacological, biochemical, and electrophysiological methods, this thesis examined how behaviors observed in mouse models of fear learning, chronic pain, and itch correspond with in vitro observations of ACC neuronal activity. Three sets of experiments are presented. The first set investigated cortical LTP-like mechanisms, and assessed whether they could mediate fear learning. These sets of experiments provide in vivo evidence that trace fear learning requires rapid, NMDA receptor dependent, cortical AMPA receptor insertion. The second set of experiments investigated the contribution of forebrain CREB-mediated transcription in behavioral manifestations of chronic pain. These experiments show that forebrain overexpression of CREB is sufficient to enhance mechanical allodynia in animal models of chronic inflammatory or neuropathic pain. Lastly, the final set of experiments show that pruritogen-induced scratching corresponds with enhanced excitatory transmission in the ACC through KA receptor modulation of inhibitory circuitry. Through investigations of multiple behaviors linked to ACC activity, this thesis presents evidence that manifestations of behavior can be observed at the molecular level, and indicates that molecular mechanisms involved in ACC synaptic activity are a good target for translational research into pathological conditions that are related to abnormal ACC activity.

Attention biases to trauma-related information contribute to symptom maintenance in Posttraumatic Stress Disorder (PTSD); this phenomenon has been observed through various behavioral studies, although findings from studies using a precise, direct bias task, the dot probe, have been mixed. PTSD neuroimaging studies have indicated atypical function in specific brain regions involved with attention bias; when viewing emotionally-salient cues or engaging in tasks that require attention, individuals with PTSD have demonstrated altered activity in brain regions implicated in cognitive control and attention allocation, including the medial prefrontal cortex (mPFC), dorsolateral prefrontal cortex (dlPFC) and amygdala. However, remarkably few PTSD neuroimaging studies have employed tasks that both measure attentional strategies being engaged and include emotionally-salient information. In the current study of attention biases in highly traumatized African-American adults, a version of the dot probe task that includes stimuli that are both salient (threatening facial expressions) and relevant (photographs of African-American faces) was administered to 19 participants with and without PTSD during functional magnetic resonance imaging (fMRI). I hypothesized that: 1) individuals with PTSD would show a significantly greater attention bias to threatening faces than traumatized controls; 2) PTSD symptoms would be associated with a significantly greater attentional bias toward threat expressed in African-American, but not Caucasian, faces; 3) PTSD symptoms would be significantly associated with abnormal activity in the mPFC, dlPFC, and amygdala during presentation of threatening faces. Behavioral data did not provide evidence of attentional biases associated with PTSD. However, increased activation in the dlPFC and regions of the mPFC in response to threat cues was found in individuals with PTSD, relative to traumatized controls without PTSD; this may reflect hyper-engaged cognitive control, attention, and conflict monitoring resources in these individuals. Additionally, viewing threat in same-race, both not other-race, faces was associated with increased activation in the mPFC. These findings have important theoretical and treatment implications, suggesting that PTSD, particularly in those individuals who have experienced chronic or multiple types of trauma, may be characterized less by top-down “deficits” or failures, but by imbalanced neurobiological and cognitive systems that become over-engaged in order to “control” the emotional disruption caused by trauma-related triggers.

Ethylene (C2H4) is a very simple molecule, a gas, and has numerous effects on the growth, development and storage life of many fruits, vegetables and ornamental crops. In higher plants, ethylene is produced from L-methionine in essentially all tissues and ACC Synthase and ACC Oxidase are the two key enzymes in the biosynthesis of ethylene. The objective of the present study was to transform tobacco (Nicotiana tabacum L. cv. Samsun) plant with partial sequence of torenia acc oxidase gene in antisense and sense orientations via Agrobacterium-mediated gene transfer system, and to analyze its effect on ethylene production in transgenic plants. Six antisense and seven sense T0 putative transgenic lines were obtained and were further analyzed with several assays. Leaf disc assay and chlorophenol red assay under selection (75 mg/L kanamycin) revealed positive results compared to the non-transformed plant. T1 generations were obtained from all putative transgenic lines. PCR analysis and Northern Blot Hybridization results confirmed the transgenic nature of T1 progeny. Furthermore, ethylene amount produced by flowers were measured with gas chromatography, which resulted in an average of 77% reduction in S7 line and 72% reduction in A1 line compared with the control flowers. These results indicated that, transgenic tobacco plants carrying torenia acc oxidase transgene both in antisense and sense orientations showed reduced ethylene production thus a possibility of flower life extension.

The effects of caffeine (250 mg) and placebo on healthy controls were studied in a double-blind, cross over study on 24 healthy subjects who performed a working memory n-back task. Reaction time and accuracy levels were tested using the n-back working memory measure in cognitive neuroscience. An experimental study tested on the 1, 2 and 3-back tasks under the placebo/coffee condition. Based on the empirical results obtained in this thesis it can be concluded that changes produced by caffeine ingestion support the hypothesis that caffeine acts as a stimulant. However, it cannot be proven that the stimulant translates into enhanced motor processes with an improvement in performance.

This essay investigates the relationship between a malfunctioning Default Mode Network (DMN) and the diagnosis of Major Depressive Disorder (MDD). A deeper understanding of how the DMN affects those brain processes which are implicated in MDD may offer new approaches to reduce the suffering of the very large number of MDD-afflicted patients. The MDD-DMN relationship has been investigated by studying scientific articles within the field of cognitive neuroscience and searching the articles for clues on how a malfunctioning DMN might correlate with the diagnosis of MDD. The essay concludes that there is much experimental evidence in support of there being a strong coupling between a malfunctioning DMN and the diagnosis of MDD.