A field-deployable instrument has been developed that isolates from an ambient aerosol population only those particles that have critical supersaturations, Sc, within a narrow, user-specified, range. This Differential Critical Supersaturation Separator (DScS) is designed to supply one or more particle size and/or composition analyzers to permit the direct examination of the factors that influence the activation properties of ambient aerosols. The DScS consists of two coupled parallel plate continuous flow thermal gradient diffusion cloud chambers housed within a single enclosure. Descriptions of instrument operation, construction and calibration data collected, when pure ammonium sulfate aerosols were injected into the DScS for operation at 0.15%< Sc<0.175%, 0.30%< Sc<0.35%, and 0.60% < Sc<0.70%, are included. Following instrument development, the DScS was deployed during March 2006 for the Megacities Impact on Regional And Global Environment (MIRAGE) field campaign in Mexico City, Mexico. Throughout the MIRAGE field campaign a Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system measured aerosol size distributions and size-resolved hygroscopicity of DScS separated aerosol. The dry diameter (Dp*) of particles sampled in the TDMA system as well as the known Sc prescribed in the DScS were combined in a modified version of Köhler Theory to make predictions of particle hygroscopicity. These predictions frequently overestimated the measurements. Further analysis of DScS separated aerosols compares the known particle Sc to a predicted particle Sc, providing insight into particle activation efficiency. Overall, the sampled aerosol exhibited properties that indicate they were more efficient at activation than Köhler Theory would predict.

A field-deployable instrument has been developed that isolates from an ambient aerosol population only those particles that have critical supersaturations, Sc, within a narrow, user-specified, range. This Differential Critical Supersaturation Separator (DScS) is designed to supply one or more particle size and/or composition analyzers to permit the direct examination of the factors that influence the activation properties of ambient aerosols. The DScS consists of two coupled parallel plate continuous flow thermal gradient diffusion cloud chambers housed within a single enclosure. Descriptions of instrument operation, construction and calibration data collected, when pure ammonium sulfate aerosols were injected into the DScS for operation at 0.15%< Sc<0.175%, 0.30%< Sc<0.35%, and 0.60% < Sc<0.70%, are included. Following instrument development, the DScS was deployed during March 2006 for the Megacities Impact on Regional And Global Environment (MIRAGE) field campaign in Mexico City, Mexico. Throughout the MIRAGE field campaign a Differential Mobility Analyzer/Tandem Differential Mobility Analyzer (DMA/TDMA) system measured aerosol size distributions and size-resolved hygroscopicity of DScS separated aerosol. The dry diameter (Dp*) of particles sampled in the TDMA system as well as the known Sc prescribed in the DScS were combined in a modified version of Köhler Theory to make predictions of particle hygroscopicity. These predictions frequently overestimated the measurements. Further analysis of DScS separated aerosols compares the known particle Sc to a predicted particle Sc, providing insight into particle activation efficiency. Overall, the sampled aerosol exhibited properties that indicate they were more efficient at activation than Köhler Theory would predict.

Thesis (M.Sc.)--York University, 2007. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 67-69) Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38756

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 151-183).

This dissertation addresses the co-evolutionary relationship between central super-massive black holes and host galaxies. This relationship is suggested by observed correlations between black hole mass (M[subscript BH]) and properties of the host galaxy bulge. We first discuss investigation of the relationship between MBH and host galaxy velocity dispersion, [sigma subscript asterisk], for quasars in the Sloan Digital Sky Survey (SDSS). We derive MBH from the broad emission line width and continuum luminosity, and [sigma subscript asterisk] from the width of narrow forbidden emission lines. For redshifts z < 0.5, our results agree with the locally-observed M[subscript BH]- [sigma subscript asterisk] relationship. For 0.5 < z < 1.2, the M[subscript BH]- [sigma subscript asterisk] relationship appears to evolve with redshift in the sense that bulges are too small for their black holes. Part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the quasar luminosity. Accounting for these biases, we find approximately a factor of two evolution in the M[subscript BH]- [sigma subscript asterisk] relationship between the present and redshift z [approximately equal] 1. The second topic involves a search for the largest velocity dispersion galaxies in the SDSS. Black holes in quasars can have M[subscript BH]exceeding 5 billion M[mass compared to the sun], implying [sigma subscript asterisk] > 500 km s−1 by the local M[subscript BH]- [sigma subscript asterisk] relationship. We present high signal-to-noise HET observations for eight galaxies at redshift z < 0.3 from the SDSS showing large [sigma subscript asterisk] while appearing to be single galaxies in HST images. The maximum velocity dispersion we find is [sigma subscript asterisk] = 444 km s−1, suggesting either that quasar black hole masses are overestimated or that the black hole - bulge relationship changes at high black hole mass. The third topic involves work contributed to co-authored papers, including: (1) evidence for recoiling black holes in SDSS quasars, (2) the [sigma][O III] - [sigma subscript asterisk] relationship in active galactic nuclei (AGN), and (3) accretion disk temperatures and continuum colors in quasars. Lastly, we discuss research in progress, including: (1) possible physical influences on the width of narrow emission lines of SDSS AGN, including the gravitational effect of the black hole, and (2) a search for binary AGN in the SDSS using double-peaked [O III] emission lines. / text

In rats, the subnuclei of the inferior olive (IO) and thalamus exist topographic spatial representation to sinusoidal horizontal linear translations along either the antero-posterior or interaural direction. To examine the effect of GABAergic neurotransmission within the vestibular nucleus on the establishment of gravity-related topographic spatial representation in relay station of the central vestibular pathway, GABAA receptor antagonist bicuculline was used to chronically perturb GABA transmission within the vestibular nucleus of postnatal rats. Implantation of bicuculline-loaded or saline-loaded Elvax slice onto the dorsal surface of vestibular nucleus was performed in P1 rats which were allowed to recover into adulthood. Fos protein expression was used as an indicator to identify central neurons responsive to horizontal linear accelerations. In stationary or labyrinthectomized rats, Fos-immunoreactive (ir) neurons were either absent or sporadically scattered throughout the IO and thalamic subnuclei, indicating that the Fos expression in these neural area was otolithic in origin. In the saline control group, Fos expression induced by horizontal antero-posterior linear acceleration was observed in both the IO and thalamus. Responsive IO subnuclei include β subnucleus of IO and dorsomedial cell column while those in the thalamus include central medial nucleus, paracentral nucleus, mediodorsal nucleus, central lateral nucleus, zona incerta and subparafascicular nucleus of thalamus. For-ir neurons responsive to horizontal interaural linear acceleration were found in those IO subnuclei and thalamic subnuclei. When compared with the saline-treated group, the number of Fos-ir IO neurons responsive to horizontal linear acceleration was significantly lower in adult rats perturbed with bicuculline at P1. Besides, the pattern of Fos expression in both the IO and thalamus was altered in adult rats pretreated with bicuculline. In the utricle-related thalamic subnuclei, the postnatal time when Fos-ir neurons were found triggered by otolithic stimulation was delayed and the number of these Fos-ir neurons was fewer in the bicuculline-treated group than those in the saline-treated group. To investigate whether there exists a critical period for postnatal establishment of topographic spatial representation in the IO and thalamus, implantation of bicuculline-loaded Elvax slice onto the vestibular nucleus was carried out in P14 rats. The topographic spatial representation in IO and thalamus of those rats were unchanged as compared with adult rats pretreated with saline at P14. These results indicate that the GABAergic neuronal circuit in the vestibular nucleus plays an important role in postnatal establishment of topographic spatial representation in the central vestibular system. Most importantly, we documented the occurrence of a postnatal critical period (between P1 and P14) during which GABAergic transmission regulated the formation of a gravity-related spatial framework in the brain. / published_or_final_version / Physiology / Master / Master of Philosophy

Inhibitory synaptic transmission within the vestibular circuits plays an essential regulatory role in coordinating vestibular functions. The maturation profile of γ- aminobutyric acid (GABA) synapses in the vestibular system remains unknown. To address this, we first used double immunohistochemistry to document the postnatal expression profile of GABAA receptors in canal-related and saccule-related vestibular nuclear neurons of rats. The proportion of Fos / GABAA receptors α1 subunit doublelabeled neurons progressively increased with age. Whole-cell patch-clamp experiments on brainstem slice preparations were also employed to characterize the developmental properties of these synapses within the medial vestibular nucleus. The frequency of GABAA receptor-mediated miniature inhibitory postsynaptic currents (IPSC) progressively increased during the first two postnatal weeks and reached a plateau thereafter. This is in agreement with an increase in sensitivity to GABAA receptor α1 subunit agonist zolpidem during the same period. The rise time and decay time however decreased by 2-fold. These results suggest that change in the composition of GABAA receptor occurs during the functional maturation of medial vestibular neurons. To further investigate whether GABA receptors contribute to synaptic plasticity in the developing vestibular nucleus, two stimulus protocols were used. Repetitive depolarizing pulses induced long-lasting decrease in the frequency of GABAA receptormediated spontaneous IPSCs between P3 and P7. The probability of inducing such frequency decline of sIPSCs decreased after the first postnatal week. High frequency stimulation on the other hand, induced long-term depression (LTD) of GABAA receptormediated evoked IPSCs between P3 and P5. The probability of inducing LTD decreased after P14. These results indicate that LTD at GABAergic synapses could be easily induced in developing medial vestibular neurons before maturation of GABAergic synaptic transmission. To examine if GABAergic transmission within the vestibular nucleus is crucial for establishment of gravity-related spatial organization, an intervention approach was adopted to perturb GABAergic transmission within the postnatal vestibular nucleus. A slice of Elvax loaded with either GABAA receptor agonist muscimol or antagonist bicuculline was inserted into the fourth ventricle and covered the bilateral vestibular nuclei at different ages. Expression of Fos protein in functionally activated neurons was used to demarcate the topographic spatial map in the inferior olive. The spatial map in subnuclei IOβ and DMCC was disturbed in each adult rat that was implanted with bicuculline- or muscimol-loaded Elvax at P1. However, no change was observed in adult rats that were pretreated with bicuculline or muscimol at P14 or P21. Vestibularrelated behavior tests were also performed. The acquisition of negative geotaxis, an otolith-related orientation reflex, was delayed in postnatal rats pretreated with bicuculline but was advanced in those rats pretreated with muscimol. Furthermore, the acquisition of motor learning, evaluated by rotarod test, was impaired in adult rats treated with bicuculline or muscimol. Taken together, our results indicated that maturation of GABAergic transmission within the vestibular nucleus play important roles in development of spatial recognition and vestibular-related behavior. / published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

No description available.

No description available.

Studies of central black holes (BHs) in nearby galaxies revealed tight correlation between the BH mass the host galaxy bulge mass, indicating a link between BH and star formation (SF) in the host galaxy. Luminous active galactic nuclei (AGN) are powered by mass accretion onto supermassive BHs. Observations of the AGNs and the SF in their host galaxies are required to understand their relation and how they establish this BH mass-galaxy bulge mass correlation over a wide range of cosmic lookback times. This thesis presents a survey of 24 μm-selected luminous AGN and their host galaxies up to z ~ 3.2. It focuses on the foreground and background broad line (Type-1) and narrow line (Type-2) AGNs of 30 massive galaxy cluster fields with total survey area of 5.2 deg², using the multi-wavelength dataset from the ultraviolet (UV) to far infrared (FIR) from the Local Cluster Substructure Survey. The AGN sample is nearly complete to a 1 mJy flux cutoff at 24 μm, and is optical-spectroscopically identified. With this dataset and the accompanying MMT/Hectospec spectroscopy survey, the properties of AGNs such as BH masses, BH accretion rates, and total luminosities, can be readily determined. Particularly, the Herschel data (100, 160, 250, 350, and 500 μm) sample the FIR peak of sources in our sample, and provide constraints on the star formation rates (SFR) in the host galaxies. For the Type 1 AGN sample, most of the systems are at z > 0.6 with luminosities > 10^45 ergs/s. Out of the 205 Type-1 AGNs, 107 are detected in at least two Herschel bands. We use AGN, stellar, and SF galaxy templates to decompose their spectral energy distributions (SEDs) from the UV to the FIR, and estimate their IR SF luminosities, AGN luminosities, and their host galaxy stellar masses. The SED decomposition reveals that a high level of SF is ubiquitous for our 24 μm-selected Type-1 AGN sample. For sources at z < 1, the stellar components from SED decomposition provide direct constraints on the stellar mass. For sources at z > 1, the BH mass-bulge stellar mass correlation is used for indirect constraints on the stellar mass. We carried out a similar analysis on the 85 Type-2 AGNs and their host galaxies up to z ~ 0.8, out of which 55 are detected in at least two Herschel bands. We reach the same conclusion as for the Type 1 AGN sample. That is, 1) These AGN host galaxies are very massive, and the vast majority of these galaxies have specific star formation rates (SSFR) consistent with those of main-sequence, star-forming galaxies rather than starbursting galaxies; 2) Most of these AGNs accrete at a rate close to 10% of Eddington; 3) We also find a strong correlation between the IR luminosity of the SF component and the AGN total luminosity, for both Type 1 and Type 2 AGNs. However, we show that the correlation could arise just because the BH mass (and hence AGN total luminosity) and the SF are both correlated with the galaxy mass, rather than requiring a causal connection between the observed rates of SF and the nuclear activity.