9,892 research outputs found
Behavior of Planaria in Instrumental Learning Paradigms
Worm behavior in instrumental learning paradigm
HgSe, a highly electronegative stable metallic contact for semiconductor devices
Schottky barriers formed by the highly electronegative substance HgSe on n-ZnS and on n-ZnSe have been characterized by capacitance-voltage and photoresponse measurements. The barriers are about 0.5 eV greater than Au barriers on these n-type substrates. HgSe contacts are stable under ambient conditions and are easily fabricated, making them attractive for device use
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Modelling the partitioning of turbulent fluxes at urban sites with varying vegetation cover
Inclusion of vegetation is critical for urban land surface models (ULSM) to represent reasonably the turbulent sensible and latent heat flux densities in an urban environment. Here the Joint UK Land Environment Simulator (JULES), an ULSM, is used to simulate the Bowen ratio at a number of urban and rural sites with vegetation cover varying between 1% and 98%. The results show that JULES is able to represent the observed Bowen ratios, but only when the additional anthropogenic water supplied into the urban ecosystem is considered. The impact of the external water use (irrigation, street cleaning), for example, on the surface energy flux partitioning can be as substantial as that of the anthropogenic heat flux on the sensible and latent heat fluxes. The Bowen ratio varies from 1-2 when the plan area vegetation fraction is between 30% and 70%. However, when the vegetation fraction is less than 20%, the Bowen ratios increase substantially (2-10) and have greater sensitivity to assumptions about external water use. As there are few long term observational sites with vegetation cover less than 30%, there is a clear need for more measurement studies in such environments
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Key conclusions of the first international urban land surface model comparison project
he first international urban land surface model comparison was designed to identify three aspects of the urban surface-atmosphere interactions: (1) the dominant physical processes, (2) the level of complexity required to model these, and 3) the parameter requirements for such a model. Offline simulations from 32 land surface schemes, with varying complexity, contributed to the comparison. Model results were analysed within a framework of physical classifications and over four stages. The results show that the following are important urban processes; (i) multiple reflections of shortwave radiation within street canyons, (ii) reduction in the amount of visible sky from within the canyon, which impacts on the net long-wave radiation, iii) the contrast in surface temperatures between building roofs and street canyons, and (iv) evaporation from vegetation. Models that use an appropriate bulk albedo based on multiple solar reflections, represent building roof surfaces separately from street canyons and include a representation of vegetation demonstrate more skill, but require parameter information on the albedo, height of the buildings relative to the width of the streets (height to width ratio), the fraction of building roofs compared to street canyons from a plan view (plan area fraction) and the fraction of the surface that is vegetated. These results, whilst based on a single site and less than 18 months of data, have implications for the future design of urban land surface models, the data that need to be measured in urban observational campaigns, and what needs to be included in initiatives for regional and global parameter databases
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Investigation of the impact of anthropogenic heat flux within an urban land surface model and PILPS-urban
Results from the first international urban model comparison experiment (PILPS-Urban) suggested that models which neglected the anthropogenic heat flux within the surface energy balance performed at least as well as models that include the source term, but this could not be explained. The analyses undertaken show that the results from PILPS-Urban were masked by the signal from including vegetation, which was identified in PILPS-Urban as being important. Including the anthropogenic heat flux does give improved performance, but the benefit is small for the site studied given the relatively small magnitude of this flux relative to other terms in the surface energy balance. However, there is no further benefit from including temporal variations in the flux at this site. The importance is expected to increase at sites with a larger anthropogenic heat flux and greater temporal variations
Kerr Correspondence 1907
A letter from the Pacific Era Publishing Company concerning Japanese students at Utah Agricultural College, a letter from Mrs. L. B. Best concerning a copy of the catalogue, and a letter from William Kerr in response of Mrs. L. B. Best\u27s letter
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Evaluation of the urban tile in MOSES using surface energy balance observations
The UK Met Office has introduced a new scheme for its urban tile in MOSES 2.2
(Met Office Surface Exchange Scheme version 2.2), which is currently implemented within
the operational Met Office weather forecasting model. Here, the performance of the urban
tile is evaluated in two urban areas: the historic core of downtown Mexico City and a light
industrial site in Vancouver, Canada. The sites differ in terms of building structures and
mean building heights. In both cases vegetation cover is less than 5%. The evaluation is
based on surface energy balance flux measurements conducted at approximately the blend-
ing height, which is the location where the surface scheme passes flux data into the atmo-
spheric model. At both sites, MOSES 2.2 correctly simulates the net radiation, but there are
discrepancies in the partitioning of turbulent and storage heat fluxes between predicted and
observed values. Of the turbulent fluxes, latent heat fluxes were underpredicted by about one
order of magnitude. Multiple model runs revealed MOSES 2.2 to be sensitive to changes in
the canopy heat storage and in the ratio between the aerodynamic roughness length and that
for heat transfer (temperature). Model performance was optimum with heat capacity values
smaller than those generally considered for these sites. The results suggest that the current
scheme is probably too simple, and that improvements may be obtained by increasing the
complexity of the model
Energy transfer in nonlinear network models of proteins
We investigate how nonlinearity and topological disorder affect the energy
relaxation of local kicks in coarse-grained network models of proteins. We find
that nonlinearity promotes long-range, coherent transfer of substantial energy
to specific, functional sites, while depressing transfer to generic locations.
Remarkably, transfer can be mediated by the self-localization of discrete
breathers at distant locations from the kick, acting as efficient
energy-accumulating centers.Comment: 4 pages, 3 figure
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