Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity (L-MIR) and the rest-frame 2-10 keV luminosity (L-X) for luminous quasars. To understand the origin of the difference in the observed L-X-L-MIR relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Bootes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed L-X-L-MIR relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different L-X-L-MIR relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 mu m, or L-6 mu m) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: log L-X = (0.84 +/- 0.03) logL(6) (mu m) /10(45)erg s(-1) + (44.60. +/- 0.01) for L-6 (mu m) < 10(44.79) erg s(-1), and log L-X (0.40 +/- 0.03) log L-6 (mu m)/10(45) erg s(-1) + (44.51 +/- 0.01) for L-6 mu m. 1044.79 erg s(-1). This suggests that the luminous type 1 quasars have a shallower LX-L6mmcorrelation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent LX-LMIRrelation and implies that assuming a linear LX-L-6 mu m relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.

An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work suggesting that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. We present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.

Modern industrial plants make use of large numbers of variable frequency drives for a variety process controls. However, a drawback of this technology is that drives are a source of harmonic currents. This work designs and models in PSCAD, an electrical system typically encountered in modern industrial operations, where the load is composed of a large percentage of voltage-source converter drives. Attempts are made to provide mitigation by employing passive shunt harmonic filters. Following the benchmarking of these filters, a shunt active filter, whose control algorithm is based on the Instantaneous Power Theory, is connected to the system. The results obtained for the active filter are compared against results obtained for the passive filters. It will be shown that a shunt active filter is more suited solution for mitigation of harmonics generated by loads dominated by drives than passive filters.

Modern industrial plants make use of large numbers of variable frequency drives for a variety process controls. However, a drawback of this technology is that drives are a source of harmonic currents. This work designs and models in PSCAD, an electrical system typically encountered in modern industrial operations, where the load is composed of a large percentage of voltage-source converter drives. Attempts are made to provide mitigation by employing passive shunt harmonic filters. Following the benchmarking of these filters, a shunt active filter, whose control algorithm is based on the Instantaneous Power Theory, is connected to the system. The results obtained for the active filter are compared against results obtained for the passive filters. It will be shown that a shunt active filter is more suited solution for mitigation of harmonics generated by loads dominated by drives than passive filters.

Increasingly, predictive models are used to support routine business de- cisions and are integral to the strategic competitive business strategies for a wide range of industries. Most often, data-driven predictive models are in- duced from training data obtained through the businesss routine operations. However, recent research on policies for intelligent information acquisitions suggests that proactive acquisition of information can improve models at a lower cost. Most active information acquisition policies are accuracy centric; they aim to identify acquisitions of training data that are particularly benefi- cial for improving the predictive accuracy of a given model. In practice, however, inferences from a predictive model are often used along with inferences from other predictive models as well as constant factors to inform arbitrarily complex decisions. In this dissertation, I discuss how these settings motivate a new kind of collaborative information acquisition (CIA) policies that exploit knowledge of the decision to allow multiple predictive models to collaboratively prioritize the prospective information acquisitions, so as to best improve the decisions they inform jointly. I present a framework for CIA policies and two specific CIA policies: CIA for binary decisions (CIA-BD), and CIA for top-ranked opportu- nities in terms of expected revenue (CIA-TR). Extensive empirical evaluations of the policies on real-world data suggest that the notion of CIA policies is indeed a valuable one. In particular, I demonstrate that these two new poli- cies lead to superior decision-making performances as compared to those of alternative policies that are either decision-centric or do not allow multiple models to collaboratively prioritize acquisitions. The performance exhibited by the CIA policies suggest that these policies are able to effectively exploit knowledge of the decisions to avoid greedy improvements in accuracy of any individual model informing the decisions; instead, they promote improvements in any one or all of the models when such improvements are likely to benefit the decisions. / text

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

<p>Recent advances in electromagnetics introduced tools that enable the creation of arti-</p><p>cial electromagnetic structures with exotic properties such as negative material pa-</p><p>rameters. The ability to express these parameters has experimentally demonstrated</p><p>using passive metamaterial structures. These structures, based on their passivity and</p><p>resonant properties, are typically associated with high loss and signicant bandwidth</p><p>limitations.</p><p>Enhancing and further exploring novel electromagnetic properties can be done</p><p>through embedding active circuits in the constitutive unit cells. Active elements</p><p>are able to supplement the passive inclusions to mitigate and overcome loss and</p><p>bandwidth limitations. The inclusion of these circuits also signcantly expands the</p><p>design space for the development of functional metamaterials and their potential</p><p>applications.</p><p>Due to the relative diculty of designing active circuits compared with passive</p><p>circuits, using active circuits in the construction of metamaterials is still an under-</p><p>developed area of research. By combining the two elds of active circuit design and</p><p>metamaterial design, we aim ll the functional active metamaterial design space.</p><p>This document provides the basis for understanding the design and synthesis of</p><p>functional active metamaterials.</p><p>To provide necessary background matter, chapter 1 will function as an introduc-</p><p>tion chapter, discussing how active electromagnetic metamaterials are created and characterized. There are also several required design techniques necessary to suc-</p><p>cessfully engineer a functional active metamaterial. The introduction will emphasize</p><p>on linking metamaterial unit cell response with RF/analog circuit design with a brief</p><p>introduction to the semiconductor physics important to aid in the understanding of</p><p>the full active metamaterial design and fabrication process.</p><p>The subsequent chapters detail our specic contributions to the eld of func-</p><p>tional active RF metamaterials. Chapter 2 introduces and characterizes a meta-</p><p>material designed to have a tunable quality factor (tunable resonant bandwidth).</p><p>This metamaterial is essentially passive but demonstrates the transistor's versatility</p><p>as a combination of tunable elements, motivating the use of embedding transistors</p><p>in metamaterials. After establishing a simple application of a transistor in a pas-</p><p>sive metamaterial, chapter 3 outlines the design and characterization of an active</p><p>metamaterial exhibiting the properties of loss cancellation and gain. Chapter 4 in-</p><p>troduces another active metamaterial with the ability to self-adapt to an incident</p><p>signal. Within the self-adapting system, several complex RF circuit systems are</p><p>simulatenously developed and implemented such as a self-oscillating mixer and a</p><p>phase locked loop. Conclusions and additional suggested future research directions</p><p>are discussed in chapter 5.</p><p>There are also several appendices attached at the end of this document that are</p><p>meant to assist future graduate students and other readers. The additional topics</p><p>include the experimental verication of a passive magnetic metamaterial acting as a</p><p>near eld parasitic, the stabilization and measurement of a tunnel diode, a discussion</p><p>on the challenges of realizing active inductors from discrete components, and a basic</p><p>strategy for creating a non-volatile metamaterial. It is my aim for these appendices</p><p>to help provide additional inspiration for future studies within the eld.</p> / Dissertation

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

The active site of porcine kidney microsomal aminopeptidase was investigated using single, multiple and EDTA inactivation kinetic studies. Good inhibitors invariably contained a zinc-coordinating group such as the mercapto moiety, which proved to be the best ligand for aminopeptidase. Due to the potency of β -mercaptoethylamine, derivatives of this compound were examined for aminopeptidase inhibition. (S)-2-amino-4-methyl-l-pentanethiol (L-leucinthiol) exhibited the largest potency and specificity towards aminopeptidase when compared against carboxypeptidase A and thermolysin, two similar zinc-peptidases. The presence of a zinc-coordination subsite, two hydrophobic pocket subsites and a second amine-binding subsite (distinct from that responsible for substrate recognition) were discerned and the binding modes of amino acid hydroxamates and mercaptoamines compared using Yonetani-Theorell inhibition kinetics. Aminopeptidase does not show virtually any stereoselectivity between L-and D-leucine hydroxamate while greater than a 1,000-fold preference is seen for L-leucinthiol over the D isomer. Also, the amino group of mercaptoamines is crucial to the binding of these inhibitors whereas that of the hydroxamate compounds does not seen to contribute much to their binding. The differences in binding between hydroxamates and mercaptoamines are postulated to be a consequence of the product analogue nature of the former and transition state analogue character of the latter. L-leucine hydroxamate is proposed to bind in a backwards orientation while the D isomer binds in the normal substrate-like position. Similarly, L-leucinthiol is proposed to bind in the same fashion as substrate. Design of future inhibitors should endeavour to: (1) lower the pᵏₐ of the α-amino group, (2) include an extended chain structure capable of binding to additional hydrophobic pockets, (3) incorporate a second amine moiety into the structure to interact with the second amine-binding subsite and (4) replace the mercapto group with a more potent zinc ligand such as the selenol group. / Thesis / Master of Science (MSc)