3,596 research outputs found
Constraining the cosmological co-evolution of galaxies and their supermassive black holes via cutting-edge jeans modelling techniques and population synthesis of active galactic nuclei
No full textGalaxy evolution is still relatively poorly understood. Specifically, star formation, mergers and the influence of a central supermassive black hole are all thought to be key drivers in regulating galaxy formation and evolution, but their relative contributions are not well constrained. Velocity dispersion (σ), a measure of the statistical variance of stellar motions in a galaxy, is known to be a key galaxy property, effectively tracing a galaxy’s gravitational potential well. The evolution of σ with cosmic time is also not well understood, despite having the potential to shed light on the relative importance of mergers versus star formation in building galaxies. σ is also known to be closely connected to the mass of the central supermassive black hole, via a tight correlation with slope of ∼ 4−6, which theories suggest could be a result of energetic winds/jets from active galactic nuclei (AGN) impacting onto the surrounding interstellar medium. In this work, I present a comprehensive semi-empirical approach to compute σ via detailed Jeans modelling, assuming, for the first time, both a constant and scale-dependent mass-to-light ratio M∗/L. I compare with a large sample of local galaxies from the MaNGA survey and find that both models can reproduce the Faber-Jackson relation and the weak dependence of σ with bulge-to-total ratio. I also explore the dynamical-to-stellar mass ratio within R ≲ Re , and show that the full dynamical mass within the effective radius can be fully accounted for by a gradient in M∗/L or a dark matter halo with an NFW profile. I then build velocity dispersion evolutionary histories, using the average histories of main progenitor dark matter haloes, assigning stellar masses, effective radii and Sersic indices via a variety of abundance matching, and empirically motivated relations. I find clear evidence for downsizing in velocity dispersion histories along the progenitor tracks, and a steady increase in velocity dispersion at fixed stellar mass with increasing redshift. I extract comparable velocity dispersion tracks from the TNG50 hydrodynamic simulation. The relative ‘flatness’ of these tracks is shown to be driven by the increasing dark matter fraction within Re, whilst showing a steeper evolution in the presence of a stellar gradient. I then show that a combination of mergers and internal star formation are likely responsible for the constant or increasing σap[M∗,z] with time. I then present new evidence for the fundamental nature of the relationship between black hole mass and σ, and show that my σ ap[M∗, z] tracks are consistent with a nearly constant and steep Mbh − σ relation at z ≲ 2, as predicted by AGN feedback models, with black hole masses derived from the LX − M∗ relation. I also show that AGN clustering can place new constraints on black hole-galaxy scaling relations, and explore the creation of AGN mock catalogs. Finally, I present an outcome of these mock catalogs, Astera, my cosmological visualization tool, which presents a real-time rendering of the large scale universe. Astera can represent an invaluable tool for survey planning and, due to its high user interactivity, also for gaming and educational and outreach activities
The resistance of cortical bone tissue to failure under cyclic loading is reduced with alendronate
No full textBisphosphonates are the most prescribed preventative treatment for osteoporosis. However, their long-term use has recently been associated with atypical fractures of cortical bone in patients who present with low-energy induced breaks of unclear pathophysiology. The effects of bisphosphonates on the mechanical properties of cortical bone have been exclusively studied under simple, monotonic, quasi-static loading. This study examined the cyclic fatigue properties of bisphosphonate-treated cortical bone at a level in which tissue damage initiates and is accumulated prior to frank fracture in low-energy situations. Physiologically relevant, dynamic, 4-point bending applied to beams (1.5 mm × 0.5 mm × 10 mm) machined from dog rib (n=12/group) demonstrated mechanical failure and micro-architectural features that were dependent on drug dose (3 groups: 0, 0.2, 1.0mg/kg/day; alendronate [ALN] for 3 years) with cortical bone tissue elastic modulus (initial cycles of loading) reduced by 21% (p<0.001) and fatigue life (number of cycles to failure) reduced in a stress-life approach by greater than 3-fold with ALN1.0 (p<0.05). While not affecting the number of osteons, ALN treatment reduced other features associated with bone remodeling, such as the size of osteons (-14%; ALN1.0: 10.5±1.8, VEH: 12.2±1.6, ×10(3) μm2; p<0.01) and the density of osteocyte lacunae (-20%; ALN1.0: 11.4±3.3, VEH: 14.3±3.6, ×10(2) #/mm2; p<0.05). Furthermore, the osteocyte lacunar density was directly proportional to initial elastic modulus when the groups were pooled (R=0.54, p<0.01). These findings suggest that the structural components normally contributing to healthy cortical bone tissue are altered by high-dose ALN treatment and contribute to reduced mechanical properties under cyclic loading conditions.NOTICE: this is the author's version of a work that was accepted for publication in Bone. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Bone, Volume 64 (July 2014) DOI: 10.1016/j.bone.2014.03.045Peer reviewe
The effect of public funding on research output: the New Zealand Marsden Fund
No full textThe Marsden Fund is the premiere funding mechanism for blue skies research in New Zealand. In 2014, $56 million was awarded to 101 research projects chosen from among 1222 applications from researchers at universities, Crown Research Institutes and independent research organizations. This funding mechanism is similar to those in other countries, such as the European Research Council.
This research measures the effect of funding receipt from the New Zealand Marsden Fund using a unique dataset of funded and unfunded proposals that includes the evaluation scores assigned to all proposals. This allows us to control statistically for potential bias driven by the Fund’s efforts to fund projects that are expected to be successful, and also to measure the efficacy of the selection process itself. We find that Marsden Funding does increase the scientific output of the funded researchers, but that there is no evidence that the final selection process is able to meaningfully predict the likely success of different proposals
American Society of Biomechanics Journal of Biomechanics Award 2013: Cortical bone tissue mechanical quality and biological mechanisms possibly underlying atypical fractures
No full textThe biomechanics literature contains many well-understood mechanisms behind typical fracture types that have important roles in treatment planning. The recent association of "atypical" fractures with long-term use of drugs designed to prevent osteoporosis has renewed interest in the effects of agents on bone tissue-level quality. While this class of fracture was recognized prior to the introduction of the anti-resorptive bisphosphonate drugs and recently likened to stress fractures, the mechanism(s) that lead to atypical fractures have not been definitively identified. Thus, a causal relationship between these drugs and atypical fracture has not been established. Physicians, bioengineers and others interested in the biomechanics of bone are working to improve fracture-prevention diagnostics, and the design of treatments to avoid this serious side-effect in the future. This review examines the mechanisms behind the bone tissue damage that may produce the atypical fracture pattern observed increasingly with long-term bisphosphonate use. Our recent findings and those of others reviewed support that the mechanisms behind normal, healthy excavation and tunnel filling by bone remodeling units within cortical tissue strengthen mechanical integrity. The ability of cortical bone to resist the damage induced during cyclic loading may be altered by the reduced remodeling and increased tissue age resulting from long-term bisphosphonate treatment. Development of assessments for such potential fractures would restore confidence in pharmaceutical treatments that have the potential to spare millions in our aging population from the morbidity and death that often follow bone fracture.Peer reviewe
Detecting intestinal ischemia using near infrared spectroscopy
No full textBlood supply to the intestine can suddenly be interrupted. Acute mesenteric intestinal ischemia often requires invasive surgery to restore blood supply to the intestine. Early correction of vascular insufficiency is the most important factor in improving patient survival when confronted with acute mesenteric intestinal ischemia. A prolonged loss of blood flow results in irreversible damage to the intestine that can lead to death. It is also imperative that dead segments of the intestines be removed. Several subjective criteria are relied upon to differentiate viable from non-viable tissue, unfortunately, these criteria can lead to an inaccurate assessment. A porcine model of intestinal ischemia was used to determine the efficacy of using near infrared (NIR) spectroscopy to find ischemic segments of the intestine and detect the onset of reperfusion following resolution of vascular occlusion. Nine segments of intestine were identified and six were assigned to three treatment groups; (1) segments undergoing no vascular manipulations, (2) segments undergoing arterial/venous occlusion and (3) segments undergoing arterial/venous occlusion followed by reperfusion. The remaining segments were used as spacers and interposed between each of the ischemia segments. A classification model, using partial least square discriminant analysis, was built on the spectra collected from the segments with no vascular manipulations and the segments that were solely subjected to arterial/venous occlusion. The spectra collected from the intestinal segments that experienced both occlusion and reperfusion were used to test the classification model. The model was able to detect and distinguish ischemic intestinal tissue with a specificity and sensitivity exceeding 80% with an overall classification accuracy of 89%. The method appears to be well suited as an intra-operative assessment method when intestinal ischemia is a concern.Michael G. Sowa, Elicia Kohlenberg, Jeri R. Payette, Lorenzo Leonardi, Michelle A. Levasseur and Christopher B. Rile
The weak dependence of velocity dispersion on disc fractions, mass-to-light ratio, and redshift: implications for galaxy and black hole evolution
No full textVelocity dispersion ( σ) is a key driver for galaxy structure and evolution. We here present a comprehensive semi-empirical approach to compute σvia detailed Jeans modelling assuming both a constant and scale-dependent mass-to-light ratio M ∗/ L . We compare with a large sample of local galaxies from MaNGA and find that both models can reproduce the Faber–Jackson (FJ) relation and the weak dependence of σon bulge-to-total (B/T) ratio (for B/T 0.25). The dynamical-to-stellar mass ratio within R R e can be fully accounted for by a gradient in M ∗/ L . We then build velocity dispersion evolutionary tracks σap [ M ∗, z] (within an aperture) along the main progenitor dark matter haloes assigning stellar masses, ef fecti ve radii, and S ́ersic indices via a variety of abundance matching and empirically moti v ated relations. We find: (1) clear e vidence for do wnsizing in σap [ M ∗, z] along the progenitor tracks; (2) at fixed stellar mass σ∝ (1 + z) 0.2 −0.3 depending on the presence or not of a gradient in M ∗/ L . We extract σap [ M ∗, z] from the TNG50 hydrodynamic simulation and find very similar results to our models with constant M ∗/ L . The increasing dark matter fraction within R e tends to flatten the σap [ M ∗, z] along the progenitors at z 1 in constant M ∗/ L models, while σap [ M ∗, z] have a steeper evolution in the presence of a stellar gradient. We then show that a combination of mergers and gas accretion is likely responsible for the constant or increasing σap [ M ∗, z] with time. Finally, our σap [ M ∗, z] are consistent with a nearly constant and steep M bh −σrelation at z 2, with black hole masses derived from the L X −M ∗relation
Reader, Authors, and the Divine Author: An Evangelical Proposal for Identifying Paul\u27s OT Citations
No full textThe article discusses several approaches for the identification of Old Testament (OT) citations made by Paul. The author-centered approach of Stanley Porter allows the investigation of verbal and thematic parallelism between the Old and the New Testament, while the reader-centered approach of Christopher Stanley, Dietrich-Alex Koch and Richard Hay, considers the impact on the reader. It highlights the method of the Divine Author-centered approach which considers the context of the citation based on the book, the Bible and the canon
The weak dependence of velocity dispersion on disc fractions, mass-to-light ratio, and redshift: implications for galaxy and black hole evolution
No full textVelocity dispersion (σ) is a key driver for galaxy structure and evolution. We here present a comprehensive semi-empirical approach to compute σ via detailed Jeans modelling assuming both a constant and scale-dependent mass-to-light ratio M*/L. We compare with a large sample of local galaxies from MaNGA and find that both models can reproduce the Faber–Jackson (FJ) relation and the weak dependence of σ on bulge-to-total (B/T) ratio (for B/T ≳ 0.25). The dynamical-to-stellar mass ratio within R ≲ Re can be fully accounted for by a gradient in M*/L. We then build velocity dispersion evolutionary tracks σap[M*, z] (within an aperture) along the main progenitor dark matter haloes assigning stellar masses, effective radii, and Sérsic indices via a variety of abundance matching and empirically motivated relations. We find: (1) clear evidence for downsizing in σap[M*, z] along the progenitor tracks; (2) at fixed stellar mass σ ∝ (1 + z)0.2−0.3 depending on the presence or not of a gradient in M*/L. We extract σap[M*, z] from the TNG50 hydrodynamic simulation and find very similar results to our models with constant M*/L. The increasing dark matter fraction within Re tends to flatten the σap[M*, z] along the progenitors at z ≳ 1 in constant M*/L models, while σap[M*, z] have a steeper evolution in the presence of a stellar gradient. We then show that a combination of mergers and gas accretion is likely responsible for the constant or increasing σap[M*, z] with time. Finally, our σap[M*, z] are consistent with a nearly constant and steep Mbh − σ relation at z ≲ 2, with black hole masses derived from the LX − M* relation
An Exploration of the Development of Huddersfield's 1970 Market Hall: Architectural Decoration with Cheap Greens; An Architect's Dream?
No full textAn exploration of the origins and development of Queensgate Market; a 1970 covered retail market in Huddersfield in the United Kingdom.
The market’s roof of glazed reinforced concrete asymmetric hyperbolic paraboloid shell umbrellas and prominent artwork have led to never ending controversy. Proposed demolition of the building in 2003 and its listing on grounds of its architectural or historic importance in 2005 accentuated the community’s dichotomy over the market’s qualities.
Can the building be better understood by examining antecedents and historical practice?
Through a review of markets and market architecture and design, hyperbolic paraboloid shell roofs engineering, retail design and public art the research aims to explore aspects of the development of Queensgate Market;
the trajectories of art, engineering and architectural practice
the transfers of awareness, knowledge, empowerment and actualisation
the mechanisms and vectors at play in such transfers; education and autodidactic learning and dissemination through publication and migration.
the connections based on proximity, employment, meeting and travel.
It was carried out by site visits, primary and secondary sources and interviews with people involved with design and construction.
Queensgate Market is identified as the unique nexus and climax in the expression of markets, hyperbolic paraboloid shells and civic art.
The study concludes that the vagaries of human migration, challenge, proximity, education and friendship are informal but important vectors in addition to technology, commercial, legislative and societal norms to the realisation of the projec
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