23,563 research outputs found
Rabies on the Last Frontier: A Phylogeographical Look at Red (Vulpus vulpus) and Arctic (Vulpus lagopus) Fox with Respect to Mitochondrial DNA and the Spatial Diffusion of Rabies
Vulpus vulpus and Vulpus lagopus are terrestrial animals that live in Alaska. They are also common carriers of the rabies virus. It has been determined that there are three different clades of rabies in Alaska being vectored by these two species of fox, but it is not clear why there are no endemic
rabies in the Interior. We are interested in
the migration patterns of Vulpus vulpus and
Vulpus lagopus, the spread and maintenance of
the rabies virus as a function of climate warming. We hypothesize that there is some
element, whether biological or geographical, that restricts the virus from spreading into
the interior and maintaining itself as much
as it does in the coastal regions of Alaska. This research provides a model for determining how the virus spreads under retreating Arctic conditions, as the globe
warms
Spatially democratic pedagogy: a pedagogical interventionto support children’s design and co-creation of classroomspace. a new trajectory for Froebel’s kindergarten spaces?
The Foundation Phase curriculum framework was introduced by the Welsh Government in 2010 (and revised in 2015). It applies to all children aged 3 to 7 years in Wales and includes a number of additional pedagogies and rights based approaches which support more participatory understandings of learning and the child (WG, 2015). However, these additional pedagogies are expected to be played out within existing constructions of space. Dominated by continuous provision, spaces are to include sand, water, writing, construction and role-play. Recently rebranded as "Learning Zones" (Taylor et al, 2015), these spaces are becoming increasingly structured around a centralised concept of space, activity and outcome, creating a paradox by framing both space and pedagogy as prescribed and not participatory.
In response this PhD explores Spatially Democratic Pedagogy (Clement, 2017) as an alternative approach to the construction of classroom space. Using Froebel's (1899) communal gardens as the pedagogical blueprint and reflecting them through recent sociomaterial (Fenwick, 2011) and democratic (Moss, 2014) understandings of learning and space, this research aims to support children in the design and co-creation of their classroom space. Its Design Based Research frame (Reimann, 2011) aims to, “solve real-world problems through the design, enactment and analysis of an intervention” (DBR Collective, 2003).
Current constructions of classroom space within the Foundation Phase were found to be complicit in restricting children and teachers' ability to participate in learning. Notably, co-creating space with children, based on their designs, appeared to offer opportunities to support participatory practice. This research contends it is the construction of space that is important when considering participatory practice within the Foundation Phase
Gas core reactors for actinide transmutation and breeder applications
This work consists of design power plant studies for four types of reactor systems: uranium plasma core breeder, uranium plasma core actinide transmuter, UF6 breeder and UF6 actinide transmuter. The plasma core systems can be coupled to MHD generators to obtain high efficiency electrical power generation. A 1074 MWt UF6 breeder reactor was designed with a breeding ratio of 1.002 to guard against diversion of fuel. Using molten salt technology and a superheated steam cycle, an efficiency of 39.2% was obtained for the plant and the U233 inventory in the core and heat exchangers was limited to 105 Kg. It was found that the UF6 reactor can produce high fluxes (10 to the 14th power n/sq cm-sec) necessary for efficient burnup of actinide. However, the buildup of fissile isotopes posed severe heat transfer problems. Therefore, the flux in the actinide region must be decreased with time. Consequently, only beginning-of-life conditions were considered for the power plant design. A 577 MWt UF6 actinide transmutation reactor power plant was designed to operate with 39.3% efficiency and 102 Kg of U233 in the core and heat exchanger for beginning-of-life conditions
Analysis of the Gas Core Actinide Transmutation Reactor (GCATR)
Design power plant studies were carried out for two applications of the plasma core reactor: (1) As a breeder reactor, (2) As a reactor able to transmute actinides effectively. In addition to the above applications the reactor produced electrical power with a high efficiency. A reactor subsystem was designed for each of the two applications. For the breeder reactor, neutronics calculations were carried out for a U-233 plasma core with a molten salt breeding blanket. A reactor was designed with a low critical mass (less than a few hundred kilograms U-233) and a breeding ratio of 1.01. The plasma core actinide transmutation reactor was designed to transmute the nuclear waste from conventional LWR's. The spent fuel is reprocessed during which 100% of Np, Am, Cm, and higher actinides are separated from the other components. These actinides are then manufactured as oxides into zirconium clad fuel rods and charged as fuel assemblies in the reflector region of the plasma core actinide transmutation reactor. In the equilibrium cycle, about 7% of the actinides are directly fissioned away, while about 31% are removed by reprocessing
Simulations of Pattern Formation in Vibrated Granular Media
We present simulations of peak pattern formation in vibrated two-dimensional
(2D) granulates and measure the dispersion relation of the pattern for various
frequencies, accelerations, cell sizes, and layer heights. We report the first
quantitative data from numerical simulations showing an interesting dependence
of the pattern wavelength on the acceleration and the system size. Our results
are related to recent experimental findings and theoretical predictions for
gravity waves.Comment: 6 pages PS-file including figures, (version accepted at Europhys.
Lett. 26.10.96
Simulations of dense granular flow: Dynamic Arches and Spin Organization
We present a numerical model for a two dimensional (2D) granular assembly,
falling in a rectangular container when the bottom is removed. We observe the
occurrence of cracks splitting the initial pile into pieces, like in
experiments. We study in detail various mechanisms connected to the
`discontinuous decompaction' of this granular material. In particular, we focus
on the history of one single long range crack, from its origin at one side
wall, until it breaks the assembly into two pieces. This event is correlated to
an increase in the number of collisions, i.e. strong pressure, and to a
momentum wave originated by one particle. Eventually, strong friction reduces
the falling velocity such that the crack may open below the slow, high pressure
`dynamic arch'. Furthermore, we report the presence of large, organized
structures of the particles' angular velocities in the dense parts of the
granulate when the number of collisions is large.Comment: Submitted to J. Phys.
Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer
International audienceWe report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer) was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976), but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection". We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL) to collapse our spectra. For the horizontal velocity spectra this scale is (zi ?o)2/3, where zi is inversion height and ?o is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z ?o)2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow. We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2). That is, the lengths of the thermal structures depend on both the lengths of the transporting eddies, ~9z, and the progressive aggregation of the plumes with height into the larger-scale structures of the CBL. This aggregation depends, in top-down fashion, on zi. The whole system is therefore highly organized, with even the smallest structures conforming to the overall requirements of the whole flow
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