With the advent of resource shared environments such as the Cloud, virtualization has become the de facto standard for server consolidation. While consolidation improves utilization, it causes performance-interference between Virtual Machines (VMs) from contention in shared resources such as CPU, Last Level Cache (LLC) and memory bandwidth. Over-provisioning resources for performance sensitive applications can guarantee Quality of Service (QoS), however, it results in low machine utilization. Thus, assuring QoS for performance sensitive applications while allowing co-location has been a challenging problem. In this thesis, we identify ways to mitigate performance interference without undue over-provisioning and also point out the need to model and account for performance interference to improve the reliability and accuracy of elastic scaling. The end goal of this research is to leverage on the observations to provide efficient resource management that is both performance and cost aware. Our main contributions are threefold; first, we improve the overall machine utilization by executing best-effort applications along side latency critical applications without violating its performance requirements. Our solution is able to dynamically adapt and leverage on the changing workload/phase behaviour to execute best-effort applications without causing excessive interference on performance; second, we identify that certain performance metrics used for elastic scaling decisions may become unreliable if performance interference is unaccounted. By modelling performance interference, we show that these performance metrics become reliable in a multi-tenant environment; and third, we identify and demonstrate the impact of interference on the accuracy of elastic scaling and propose a solution to significantly minimise performance violations at a reduced cost. / <p>QC 20160927</p>

Thesis advisor: Sara Cordes / Human infants show relatively sophisticated abilities to track and use proportional information. However, by the age of 6, children tend to make predictable errors in their proportional reasoning and later encounter significant challenges in many aspects of formal fraction learning. Thus, one of the central questions motivating this research is to identify the factors leading to these difficulties, in light of evidence of early intuitions about these concepts. In the current dissertation, I address this question by investigating the tradeoff between attending to proportional magnitude information and discrete numerical information about the components (termed “numerical interference”) across both spatial (i.e., area models, number lines) and symbolic (fractions, decimals) representations of proportion information. These explorations focus on young children (5-7 year olds) who have yet to receive formal fraction instruction, older children (9-12 year olds) who are in the process of learning these concepts, and adults who have already learned formal fractions. In Project 1, I investigated how older children and adults map between symbolic and spatial representations, particularly focusing on their strategies in highlighting componential information versus magnitude information when solving these mapping tasks. In Projects 2 and 3, I explore the malleability of individual differences in this numerical interference in 4- to 7-year-old children. Across the three projects, I suggest that although numerical interference does impact proportional reasoning, this over-attention to number can be reduced through modifying early experiences with proportional information. These findings have implications for education and the way we conceptualize numerical interference more generally. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

PhD, Faculty of Health Sciences, University of the Witwatersrand, 2009 / Chronic infection with the hepatitis B virus (HBV) is a major risk factor for cirrhosis and hepatocellular carcinoma, which is the sixth most common cancer worldwide. Available treatment for chronic HBV infection has limited efficacy in preventing associated complications. The compact and multifunctional nature of the viral genome limits its mutability making HBV an ideal candidate for therapy based on nucleic acid hybridisation. The potent and specific gene silencing that can be achieved with RNA interference (RNAi) has fueled interest in exploiting this pathway as a therapeutic modality. Synthetic and expressed RNA sequences have been used to activate RNAi. These engineered sequences mimic natural substrates of the RNAi pathway, which allows them to enter and reprogramme the pathway to effect silencing of intended targets. Tradionally expressed RNAi activators have been transcribed as short hairpin RNA (shRNA) sequences from RNA polymerase III (Pol III) promoters. These shRNA mimic precursor microRNA (pre-miRNA) and consequently enter the RNAi pathway at a relatively late stage. Overexpression of shRNA sequences from Pol III promoters, specifically the U6 promoter, has been associated with toxic side effects and has raised concerns about the use of expressed RNAi activators. Another concern of developing therapeutic RNAi expression cassettes is the emergence of HBV mutants that are resistant to silencing by a single expressed RNAi effecter. These points have highlighted the need for the development expressed RNAi activators that are effective at low concentrations and capable of combinatorial silencing. To address these issues the aim of this study was to assess the feasibility of anti HBV effecter sequences that mimic an early substrate (viz. primary miRNA or pri-miRNA) of the RNAi pathway. Pri-miRNA expression is typically under the transcriptional control of Pol II promoters. Consequently RNAi activators that Abstract - xi - mimic pri-miRNA, so-called pri-miR shuttles, may be expressed from Pol II promoters. Initially a panel of shRNA expression cassettes driven by a Pol III promoter was constructed and silencing of HBV replication assessed. Pri-miR shuttles were then designed by incorporating guide sequences of the most effective anti HBV U6 shRNA into naturally occurring pri-miR-122 and pri-miR-31. Potent inhibition of viral replication was observed with both Pol III and Pol II-driven pri-miR shuttle expression cassettes in vitro and in vivo. Subsequently liver-specific pri-miR-122 and multimeric pri-miR-31 shuttle expression cassettes were created. Pri-miR-122 shuttle sequences expressed from the alpha-1 antitrypsin promoter and HBV basic core promoter exhibited the best liver-specific silencing. Polycistronic pri-miR-31 shuttle sequences were shown to produce multiple RNAi activators capable of silencing multiple target sequences. Silencing by the pri-miR shuttle sequences was independent of toxic effects that arise from induction of the interferon response or saturation of the endogenous miRNA pathway. Pri-miR shuttles clearly represent an improved option for the use of expressed shRNA and brings therapeutic RNAi technology a step closer to clinical application.

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We present a theoretical analysis of surface-plasmon-mediated mode-coupling in a planar thin film metal/insulator stack. The spatial overlap of a surface plasmon polariton (SPP) and a waveguide mode results in a Fano interference analog. Tuning of the material parameters effects the modes and output fields of the system. Lastly, the intensity and phase sensitivity of the system are compared to a standard surface plasmon resonance (SPR). We begin with background information on Fano interference, an interference effect between two indistinguishable pathways. Originally described for autoionization, we discuss the analogs in other systems. We discuss the features of Fano interference in the mode diagrams, and the Fano resonance observed in the output field. The idea of a geometric Fano resonance (GFR) occurring in the angular domain is presented. Background information on surface plasmon polaritons is covered next. The dielectric properties of metals and how they relate to surface plasmons is first reviewed. The theoretical background of SPPs on an infinite planar surface is covered. The modes of a two planar interface metal/insulator stack are reviewed and the leaky properties of the waveguide are shown in the reflectance. We solve for modes of a three interface metal/insulator stack and shows an avoided crossing in the modes indicative of Fano interference. We observe the asymmetric Fano resonance in the angular domain in the reflectance. The tunability of the material parameters tunes the GFR of the system. The GFR tuning is explored and different Fano lineshapes are observed. We also observe a reversal of the asymmetry Fano lineshape, attributed to the relate phase interactions of the non-interacting modes. The phase of the GFR is calculated and discussed for the variations of the parameters. The reflected field is explored as the insulator permittivities are varied. As the waveguide permittivity is varied, we show there is little response from the system. As the exterior permittivity is varied, the reflectance exhibits the geometric Fano resonance and the tunability of the lineshape is explored. Finally, we calculate the sensitivities of our metal/insulator stack to changes in the permittivity and compare them to the sensitivities of SPRs.

Ctenocephalides felis is a major pest of companion animals worldwide. This project aimed to generate novel genetic resources for C. felis and develop tools to aid drug-target identification and validation. Sample handling methods were assessed and candidate reference genes validated, to ensure quality of RNA samples and reliable gene expression normalisation. Piercing C. felis samples prior to storage in RNAlater ensured RNA integrity was maintained over time. Glyceraldehyde 3-phosphate dehydrogenase , 60S ribosomal protein L19 and elongation factor-1α were demonstrated as stable reference genes across all comparisons tested. A C. felis transcriptome encompassing multiple developmental stages, sexes and tissues was sequenced and de novo assemblies produced with two assemblers, Trinity and Oases. Each assembly contained >100000 contigs. Annotation of the assemblies generated functional insight, such as top BLAST hits, GO annotations and signal peptide predictions. The Trinity assembly was deemed the highest quality and searched for genes of interest, involved in development. Expression analysis of selected transcripts across stadia gave insight into developmental processes, and demonstrated the utility of the transcriptome. This study was the first to demonstrate that C. felis can mount an RNAi response upon exposure to dsRNA. Knockdown of glutathione S-transferase σ (GSTσ), was demonstrated in adult C. felis: ≈80 % knockdown following microinjection of dsGSTσ; ≈64 % knockdown after soaking in dsGSTσ; ≈96 % knockdown after continuous feeding on dsGSTσ. RNAi machinery was identified in C. felis. siRNAi pathway components, Dicer 2 and Argonaute 2, were upregulated following dsRNA exposure. Dicer 2 was knocked-down by soaking in dsDicer2, although results of an “RNAi of RNAi” experiment were inconclusive. Transcripts encoding machinery putatively involved in dsRNA uptake and breakdown were also identified. Through these studies, this project has generated novel insights into C. felis biology and opened up new avenues for research.

It is necessary for radars to suppress interferences to near the noise level to achieve the best performance in target detection and measurements. In this dissertation work, innovative signal processing approaches are proposed to effectively mitigate two of the most common types of interferences: jammers and clutter. Two types of radar systems are considered for developing new signal processing algorithms: phased-array radar and multiple-input multiple-output (MIMO) radar. For phased-array radar, an innovative target-clutter feature-based recognition approach termed as Beam-Doppler Image Feature Recognition (BDIFR) is proposed to detect moving targets in inhomogeneous clutter. Moreover, a new ground moving target detection algorithm is proposed for airborne radar. The essence of this algorithm is to compensate for the ground clutter Doppler shift caused by the moving platform and then to cancel the Doppler-compensated clutter using MTI filters that are commonly used in ground-based radar systems. Without the need of clutter estimation, the new algorithms outperform the conventional Space-Time Adaptive Processing (STAP) algorithm in ground moving target detection in inhomogeneous clutter. For MIMO radar, a time-efficient reduced-dimensional clutter suppression algorithm termed as Reduced-dimension Space-time Adaptive Processing (RSTAP) is proposed to minimize the number of the training samples required for clutter estimation. To deal with highly heterogeneous clutter more effectively, we also proposed a robust deterministic STAP algorithm operating on snapshot-to-snapshot basis. For cancelling jammers in the radar mainlobe direction, an innovative jamming elimination approach is proposed based on coherent MIMO radar adaptive beamforming. When combined with mutual information (MI) based cognitive radar transmit waveform design, this new approach can be used to enable spectrum sharing effectively between radar and wireless communication systems. The proposed interference mitigation approaches are validated by carrying out simulations for typical radar operation scenarios. The advantages of the proposed interference mitigation methods over the existing signal processing techniques are demonstrated both analytically and empirically.

<p>For multispectral Remote Sensing (RS) image analysis, a big problem is that original dataalways include Clouds-Interference (CI). Especially in the bad weather conditions, the CI is evidentin RS image. So during the pre-processing of RS image, the CI should be reduced as much aspossible. In this paper, reducing CI is researched as the central problem, so that much Ground-Objects Feature (GOF) can be obtained. An analysis about the clouds reflection in differentSpectral-Bands (SBs) was done based on optical theory and early researches. Moreover, therelationships between clouds reflection and ground-objects reflection are presented to understandwhat the Digital Number (DN) represented in each SB, and to reduce the impact of CI the Same DNSpectral Matching Method (SDN-SMM) based on the multispectral application is applied. Finally,two cases are tested using Matlab Programme to indicate the rationality and practicability of SDNSMM.About SDN-SMM, some advantages and disadvantages are concluded through discussion onfinal results. The method can be used in any kind of multispectral sensors image with simplecalculation, while, the original data of clouds-free region will not be changed. However, the qualityof CI reduction depends on the precision of clouds identification and the SB which is used forspectral position relationship creating. In the end of this paper, the improvement is also presentedfor the future work.</p>

A method and apparatus are presented for generating suppressed carrier digital clock signals. These clock signals have the advantage of being broad band in nature and thus exhibiting lower power spectral density. Structures or systems utilizing such clock signals would be less likely to create electromagnetic noise of sufficient intensity to interfere with radio frequency systems and services. The apparatus requires only digital logic devices, rather than the analog devices required for frequency- or phase-modulated spread spectrum clock generators. The method provides the opportunity to synchronously demodulate the clock, thus restoring the original narrow band clock signal where required. The apparatus was implemented in a programmable gate array using 20 MHz and 33.33 MHz fundamental clocks. Measurements of the resulting electronic spectra and clock jitter are reported. / Graduation date: 1999

Conducted Electromagnetic Interference (EMI) is a major cause of concern in switchmode power supplies (SMPS) which commonly use standard pulsewidth modulation (PWM). In this thesis, Sigma-Delta (����) modulation is proposed as an alternative switching technique to reduce conducted EMI from SMPS. The result of using ���� modulation is a spread in the spectrum of the conducted emissions so that large concentrations of power at discrete frequencies are avoided. Experimental time-domain waveforms and spectra of the switching function from first-order and second-order ���� modulators are presented to prove the viability of the scheme in EMI mitigation. These modulators are then applied to an off-the-shelf computer power supply and experimental results using FCC-specified methods show a reduction of roughly 5-10dB in EMI emissions over standard PWM modulators. / Graduation date: 1999