The properties of discrete X-ray sources in star-forming galaxies

Observations of starburst galaxies have revealed a large number of point-like X-ray sources located within these systems, including active galactic nuclei (AGN), X-ray binaries (XRBs), and utraluminous X-ray sources (ULXs). In this thesis we investigate the physical properties of a variety of these objects using both their X-ray emission characteristics and their optical counterparts, in order to better understand the accretion physics of such objects, and the environments in which they are found. This work begins with a study of 3 moderate-redshift (z ~ 0.1) X-ray bright (> 10^42 erg s^-1) galaxies, all of which display no clear signs of the presence of an AGN in the optical band. Given the high X-ray luminosities of these objects, they must either be the most X-ray luminous starburst galaxies known; or they must harbour a hidden AGN. We use new, pointed observations of the galaxies to determine their detailed X-ray characteristics, and demonstrate that each X-ray source is consistent with an AGN. The most likely explanation for the lack of AGN signatures in the optical spectra of these galaxies is that the AGN emission lines are being diluted by star formation signatures from within the host galaxies. Next, we present age constraints on 13 bright XRBs located within the high-metallicity drop-through ring galaxy NGC 922. While less than half the X-ray sources are located close to recent star formation as traced by Hα emission, the majority of sources are associated with star clusters, that we are able to age on the basis of their optical colours. We find that the sources that are closest to clusters tend to also have the youngest counterpart clusters and, in most cases, are close to H$\alpha$ emission, placing a limit of < 10 Myrs on their age, while those with greater distances to star clusters are also significantly older. We also investigate the possibility that the X-ray sources were ejected from their parent clusters, either by dynamical interactions, or by supernova kicks. An important caveat to the results of this work is that the a number of sources may have associated clusters that are highly extinguished and are therefore undetectable in the optical band. Finally, we present a study of the 8 brightest X-ray point-sources in the prototypical starburst galaxy M82, using the rich data set afforded to us by a ~ 480 ks Chandra observation of the galaxy. From our investigation, we find that the sources with X-ray luminosities < 10^39 erg s^-1 are heterogeneous, but all display X-ray properties that are typically observed in canonically accreting back hole binaries. A possible bi-modality is seen in accretion states between the more luminous and less luminous sources in this subset of our sample. The majority of these sources show significant long-term variability, with one of the sources being identified as a transient candidate. The three brightest sources in our sample, all of which are known ULXs, display long-term variability and spectral characteristics consistent with previous observations. This work demonstrates the rich potential for future studies of the diverse X-ray binary populations in nearby galaxies

Non Destructive Determination Of Elastic Moduli By Two Dimensional Fourier Transformation And Laser Ultrasonic Technique

Broadband laser ultrasonics and two dimensional Fourier transformation are used to characterize the properties of varieties of foils and plates. Laser ultrasonics generation is achieved by use of a pulsed laser which deposits pulsed laser energy on the surface of the specimen. The displacement amplitude of the resulting broadband ultrasonic modes are monitored using a two wave mixing photo-refractive interferometer. By applying a two dimensional Fourier transformation to the detected spatial and temporal displacement waveforms, the images of density of state (DOS) for the excited ultrasounds are obtained. Results are presented for a 150 um thick paper sample, a 52.8 um stainless steel foil and a 1.27 mm thick aluminum plate. The DOS image demonstrates the ability to measure the properties of each generated ultrasonic modes and provides a direct, non destructive, measure of elastic moduli of the tested specimensComment: Laser ultrasonics, Fourier transformation, NDT&E, Lamb waves, plate mode

Structuring International Financial Support for Climate Change Mitigation in Developing Countries

In the Copenhagen Accord of December 2009, developed countries agreed to provide start-up finance for adaptation in developing countries and expressed the ambition to scale this up to $100 billion per year by 2020. The financial mechanisms to deliver this support have to be tailored to country and sector specific needs so as to enable domestic policy processes and self sustaining business models, and to limit policy risk exposure for investors while complying with budgetary constraints in OECD countries. This paper structures the available financial mechanisms according to the needs they can address, and reports on experience with their application in bilateral and multilateral settings.Financial mechanism, risk guarantee, development, climate policy

Bioaccumulation of heavy metals concentration in some selected cereals grown near illegal mine Sites at Poyentanga in Wa of the Upper West Region, Ghana

The contamination of cereals by heavy metals due to illegal mining activities in most farming communities has been a major challenge to food production in Ghana. The research is thus to examine bio-accumulation of heavy metals (Cadmium (Cd), Arsenic (As), Iron (Fe), Lead (Pd) and Zinc (Zn)) concentration in Maize and Millet grown near illegal mining sites at Poyentanga. The study area was divided into five farming zones (farm 1, 2, 3, 4 and 5) and soil and crop samples were taken from each of the zones to the laboratory for analysis using the Atomic Absorption Spectrometer and the results compared to World Health Organization (WHO) permissible limits. The results indicate presence of the selected heavy metals in the cereals and soils sampled from the community. Cd, Pb and Fe concentrations in the cereals were found to be above the WHO permissible limits whereas As and Zn concentrations were below. The soil concentrations of all the five heavy metals were extremely below the WHO permissible limits. It was also observed that farms near the mining sites have higher concentrations with the concentration in the maize being lower than that of Millet. The contamination levels in both cereals are as follows: Zn As Fe Pb Cd. The bioaccumulation ratio indicated that Cd, As and Pb levels were higher in Millet whereas Fe and Zn were highest in the Maize. These results therefore show that the consumption of these cereals for a very long time could have adverse health effect on the community and an indication that activities of illegal mining could thus affect the quality and safety of food produced in many farming communities. The research was concluded with recommendations to improve agricultural activities in such communities

General Effective Field Theory of Teleparallel Gravity

We construct the Effective Field Theory (EFT) of the teleparallel equivalent of general relativity (TEGR). Firstly, we present the necessary field redefinitions of the scalar field and the tetrads. Then we provide all the terms at next-to-leading-order, containing the torsion tensor and its derivatives, and derivatives of the scalar field, accompanied by generic scalar-field-dependent couplings, where all operators are suppressed by a scale $\Lambda$. Removing all redundant terms using the field redefinitions we result to the EFT of TEGR, which includes significantly more terms comparing to the EFT of General Relativity. Finally, we present an application in a cosmological framework. Interestingly enough, although GR and TEGR are completely equivalent at the level of classical equations, we find that their corresponding EFTs possess minor but non-zero differences. Hence, we do verify that at higher energies the excitation and the features of the extra degrees of freedom are slightly different in the two theories, thus making them theoretically distinguishable. Nevertheless, we mention that these differences are suppressed by the heavy mass scale $\Lambda$ and thus it is not guaranteed that they could be measured in future experiments and observations.Comment: 16 pages, comments are welcom

Low-Frequency Measurements of Seismic Moduli and Attenuation in Antigorite Serpentinite

Laboratory measurements of seismic moduli and attenuation in antigorite serpentinite at a confining pressure of 200 MPa and temperatures up to 550 °C provide new results relevant to the interpretation of geophysical data in subduction zones. A polycrystalline antigorite specimen was tested via forced oscillations at small strain amplitudes and seismic frequencies (millihertz to hertz). The shear modulus has a temperature sensitivity, ∂G/∂T, averaging −0.017 GPa/K. Increasing temperature above 500 °C results in more intensive shear attenuation ( urn:x-wiley:grl:media:grl58579:grl58579-math-0001) and associated modulus dispersion, with urn:x-wiley:grl:media:grl58579:grl58579-math-0002 increasing monotonically with increasing oscillation period and temperature. This “background” relaxation is adequately captured by a Burgers model for viscoelasticity and possibly results from intergranular mechanisms. Attenuation is higher in antigorite ( urn:x-wiley:grl:media:grl58579:grl58579-math-0003 at 550 °C and 0.01 Hz) than in olivine ( urn:x-wiley:grl:media:grl58579:grl58579-math-0004 below 800 °C), but such contrast does not appear to be strong enough to allow robust identification of antigorite from seismic models of attenuation only

EEVEE : the Empathy-Enhancing Virtual Evolving Environment

Empathy is a multifaceted emotional and mental faculty that is often found to be affected in a great number of psychopathologies, such as schizophrenia, yet it remains very difficult to measure in an ecological context. The challenge stems partly from the complexity and fluidity of this social process, but also from its covert nature. One powerful tool to enhance experimental control over such dynamic social interactions has been the use of avatars in virtual reality (VR); information about an individual in such an interaction can be collected through the analysis of his or her neurophysiological and behavioral responses. We have developed a unique platform, the Empathy-Enhancing Virtual Evolving Environment (EEVEE), which is built around three main components: (1) different avatars capable of expressing feelings and emotions at various levels based on the Facial Action Coding System (FACS); (2) systems for measuring the physiological responses of the observer (heart and respiration rate, skin conductance, gaze and eye movements, facial expression); and (3) a multimodal interface linking the avatar's behavior to the observer's neurophysiological response. In this article, we provide a detailed description of the components of this innovative platform and validation data from the first phases of development. Our data show that healthy adults can discriminate different negative emotions, including pain, expressed by avatars at varying intensities. We also provide evidence that masking part of an avatar's face (top or bottom half) does not prevent the detection of different levels of pain. This innovative and flexible platform provides a unique tool to study and even modulate empathy in a comprehensive and ecological manner in various populations, notably individuals suffering from neurological or psychiatric disorders.Canadian Foundation for Innovation Natural Sciences and Engineering Research Council of Canada to PLJ Canadian Institutes of Health Research Fonds de recherche du Québec – Sant