4,780 research outputs found
Galaxy size trends as a consequence of cosmology
We show that recently documented trends in galaxy sizes with mass and
redshift can be understood in terms of the influence of underlying cosmic
evolution; a holistic view which is complimentary to interpretations involving
the accumulation of discreet evolutionary processes acting on individual
objects. Using standard cosmology theory, supported with results from the
Millennium simulations, we derive expected size trends for collapsed cosmic
structures, emphasising the important distinction between these trends and the
assembly paths of individual regions. We then argue that the observed variation
in the stellar mass content of these structures can be understood to first
order in terms of natural limitations of cooling and feedback. But whilst these
relative masses vary by orders of magnitude, galaxy and host radii have been
found to correlate linearly. We explain how these two aspects will lead to
galaxy sizes that closely follow observed trends and their evolution, comparing
directly with the COSMOS and SDSS surveys. Thus we conclude that the observed
minimum radius for galaxies, the evolving trend in size as a function of mass
for intermediate systems, and the observed increase in the sizes of massive
galaxies, may all be considered an emergent consequence of the cosmic
expansion.Comment: 14 pages, 13 figures. Accepted by MNRA
Earliest Directly-Dated Human Skull-Cups
The use of human braincases as drinking cups and containers has extensive historic and ethnographic documentation, but archaeological examples are extremely rare. In the Upper Palaeolithic of western Europe, cut-marked and broken human bones are widespread in the Magdalenian (∼15 to 12,000 years BP) and skull-cup preparation is an element of this tradition
The Vibration Ring
The vibration ring was conceived as a driveline damping device to prevent structure-borne noise in machines. It has the appearance of a metal ring, and can be installed between any two driveline components like an ordinary mechanical spacer. Damping is achieved using a ring-shaped piezoelectric stack that is poled in the axial direction and connected to an electrical shunt circuit. Surrounding the stack is a metal structure, called the compression cage, which squeezes the stack along its poled axis when excited by radial driveline forces. The stack in turn generates electrical energy, which is either dissipated or harvested using the shunt circuit. Removing energy from the system creates a net damping effect. The vibration ring is much stiffer than traditional damping devices, which allows it to be used in a driveline without disrupting normal operation. In phase 1 of this NASA Seedling Fund project, a combination of design and analysis was used to examine the feasibility of this concept. Several designs were evaluated using solid modeling, finite element analysis, and by creating prototype hardware. Then an analytical model representing the coupled electromechanical response was formulated in closed form. The model was exercised parametrically to examine the stiffness and loss factor spectra of the vibration ring, as well as simulate its damping effect in the context of a simplified driveline model. The results of this work showed that this is a viable mechanism for driveline damping, and provided several lessons for continued development
EPHA3 (EPH receptor A3)
Review on EPHA3 (EPH receptor A3), with data on DNA, on the protein encoded, and where the gene is implicated
Peer mentorship and positive effects on student mentor and mentee retention and academic success
This study examined how the introduction of peer mentorship in an undergraduate health and social welfare programme at a large northern university affected student learning. Using an ethnographic case study approach, the study draws upon data collected from a small group of mentors and their mentees over a period of one academic year using interviews, reflective journals, assessment and course evaluation data.
Analysis of the data collected identified a number of key findings: peer mentorship improves assessment performance for both mentee and mentor; reduces stress and anxiety, enhances participation and engagement in the academic community, and adds value to student outcomes
Russia-UK collaboration in paleontology: past, present, and future
There is a long history of collaboration between Russia and the United Kingdom in paleontology. This began, arguably, in 1821, with the seminal work by William Fox-Strangways, who produced a geological map of the area around St Petersburg. Most famously, Roderick Murchison carried out extensive surveying and observations throughout European Russia in 1840 and 1841, and published a major monograph on geology and paleontology of European Russia in 1845. Since then, and continuing today, there have been many fruitful collaborations on Precambrian life, Paleozoic marine organisms, terrestrialization of plants and vertebrates, the Permian–Triassic mass extinction, fossil mammals, human evolution, and conservation paleobiology
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