X-rays From Quasars and Active Galaxies

Features of quasars and active galactic nuclei are discussed and include: the nature of the power source, the radiation processes, and the mechanism for the formation and collimation of long-lived jets of matter observed to emanate from the center of these of these objects. The phenomena that produce X-rays are highlighted

K to pi pi Amplitudes at Unphysical Kinematics Using Domain Wall Fermions

The use of chiral perturbation theory in extracting physical K to pi pi matrix elements from matrix elements calculated at unphysical kinematics is outlined. In particular, the possibility of utilizing pions with non-zero momentum in the final state, and of using partial quenching is discussed. Preliminary (not physically normalized) Delta I=3/2 (27,1) K to pi pi matrix elements are calculated on the RBC/UKQCD $24^3 \times 64$, $L_s=16$ lattices, using 2+1 dynamical flavors and domain wall fermions, with an inverse lattice spacing of $a^{-1}=1.729(28) GeV$. Effective mass plots are presented for a light sea quark mass of $m_l^{sea}=0.005$, and various valence quark masses. The plateaux are fit and $E_{\pi\pi}-m_K$ is extracted.Comment: 7 pages, 4 figures, Talk presented at the XXV International Symposium on Lattice Field Theory, July 30 - August 4 2007, Regensburg, German

A sore red eye with systemic involvement

The study of happiness has long been a playground for philosophical speculation. By lack of empirical measures of happiness, it was not possible to check propositions about the matter. In the late 20th century, survey-research methods introduced by the social sciences have brought a break-through. Dependable measures of happiness have developed, by means of which a significant body of knowledge has evolved

The International Scientific Series and the Communication of Darwinism?

This thesis notes that there is a lack of systematic research investigating segregation patterns based on how public space is used and frequented by citizens. In order for understanding of urban segregation to reach beyond residential segregation, the extent to which public space facilitates co-presence between social groups is a key issue. The main concern in this thesis is to arrive at a deeper understanding of the critical role urban form plays in terms of co-presence in public space and in extension for social segregation. The argument builds on knowledge from other fields, arguing that co-presence is of utmost importance for societal processes: by sharing space and being co-present with others, which does not necessarily imply focused interaction, we gain information and knowledge from our fellow citizens and participate in processes that negotiate social structures, acceptable behaviours and identities. The sharing of space thus becomes a central part of ‘being in society’. It is furthermore through public space that material urban resources are accessible, an access that is dependent on both the location of the amenities in space but also the distribution of space, as structured and shaped by urban form, which creates the actual experience of access through space. Segregation is primarily defined as a social problem. However, in this thesis, it is made clear that it is also a spatial problem. While also broadening the conceptualisation of segregation, the main focus has been upon the role of the built environment. The socio-spatial link builds on social theories. However, these theories are weak when it comes to explaining where co-presence occurs. Addressing the spatial side of the problem, the thesis primarily builds on the architectural theory of space syntax that exactly aims to study the space-society relationship from the viewpoint of space and provides empirical evidence for the correspondence between urban form – as it is shaped by urban design and architecture – and the creation of co-presence as well as variations in its intensity and its constitution. In addition, key questions such as what people may have access to ‘just around the corner’ in terms of human resources or other urban amenities are elaborated. The distinct variations found between neighbourhoods are argued both to enrich the discussion on social exclusion and unequal living conditions and inform future urban planning and design. The thesis demonstrates that specific configurational properties have great impact on the pattern of co-presence. More specifically, it is found that a segregation of public space, a limited spatial reach and an uneven distribution of spatial centrality appears not to favour an exchange between neighbourhoods or access to urban resources across the city – findings that are highly critical for the urban segregation issue. Detailed configurational analysis of Stockholm reveals the performative aspects of different urban layouts related not only to local circumstances and character but, more importantly, to the further context of such layouts. Increased knowledge of how spatial configuration relates to social practices offers new insight into how different neighbourhoods and urban layouts perform socially and increases understanding of the social implications of spatial configuration. The findings of this study are argued to open up theoretical developments that address the social and political dimension of urban design with greater precision. Not least, this knowledge can influence public debate. The knowledge produced can furthermore be used in urban design practice and anti-segregation initiatives, identifying whether spatial interventions can make a contribution and if so, what physical interventions respond to the social ends in question, where the ultimate aim is an urban design that not only builds cities but societies too.QC 20131108</p

Automated Lensing Learner: Automated Strong Lensing Identification with a Computer Vision Technique

Forthcoming surveys such as the Large Synoptic Survey Telescope (LSST) and Euclid necessitate automatic and efficient identification methods of strong lensing systems. We present a strong lensing identification approach that utilizes a feature extraction method from computer vision, the Histogram of Oriented Gradients (HOG), to capture edge patterns of arcs. We train a supervised classifier model on the HOG of mock strong galaxy-galaxy lens images similar to observations from the Hubble Space Telescope (HST) and LSST. We assess model performance with the area under the curve (AUC) of a Receiver Operating Characteristic (ROC) curve. Models trained on 10,000 lens and non-lens containing images images exhibit an AUC of 0.975 for an HST-like sample, 0.625 for one exposure of LSST, and 0.809 for 10-year mock LSST observations. Performance appears to continually improve with the training set size. Models trained on fewer images perform better in absence of the lens galaxy light. However, with larger training data sets, information from the lens galaxy actually improves model performance, indicating that HOG captures much of the morphological complexity of the arc finding problem. We test our classifier on data from the Sloan Lens ACS Survey and find that small scale image features reduces the efficiency of our trained model. However, these preliminary tests indicate that some parameterizations of HOG can compensate for differences between observed mock data. One example best-case parameterization results in an AUC of 0.6 in the F814 filter image with other parameterization results equivalent to random performance.Comment: 18 pages, 14 figures, summarizing results in figure

Fundamental studies in X-ray astrophysics

An analytical model calculation of the ionization structure of matter accreting onto a degenerate dwarf was carried out. Self-consistent values of the various parameters are used. The possibility of nuclear burning of the accreting matter is included. We find the blackbody radiation emitted from the stellar surface keeps hydrogen and helium ionized out to distances much larger than a typical binary separation. Except for low mass stars or high accretion rates, the assumption of complete ionization of the elements heavier than helium is a good first approximation. For low mass stars or high accretion rates the validity of assuming complete ionization depends sensitivity on the distribution of matter in the binary system

Effect of vasopressin 1b receptor blockade on the hypothalamic-pituitary-adrenal response of chronically stressed rats to a heterotypic stressor

Exposure to chronic restraint (CR) modifies the hypothalamic–pituitary–adrenal (HPA) axis response to subsequent acute stressors with adaptation of the response to a homotypic and sensitization of the response to a heterotypic stressor. Since vasopressin (AVP) activity has been reported to change during chronic stress, we investigated whether this was an important factor in HPA facilitation. We therefore tested whether vasopressin 1b receptor (AVPR1B) blockade altered the ACTH and corticosterone response to heterotypic stressors following CR stress. Adult male rats were exposed to CR, single restraint, or were left undisturbed in the home cage. Twenty-four hours after the last restraint, rats were injected with either a AVPR1B antagonist (Org, 30 mg/kg, s.c.) or vehicle (5% mulgofen in saline, 0.2/kg, s.c.) and then exposed to either restraint, lipopolysaccharide (LPS) or white noise. CR resulted in the adaptation of the ACTH and corticosterone response to restraint and this effect was not prevented by pretreatment with Org. Although we found no effect of CR on LPS-induced ACTH and corticosterone secretion, both repeated and single episodes of restraint induced the sensitization of the ACTH, but not corticosterone response to acute noise. Pretreatment with Org reduced the exaggerated ACTH response to noise after both single and repeated exposure to restraint